Patent Publication Number: US-10775873-B2

Title: Performing power management in a multicore processor

Description:
This application is a continuation of U.S. patent application Ser. No. 14/621,709, filed Feb. 13, 2015, the content of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments relate to power management of a system, and more particularly to power management of a multicore processor. 
     BACKGROUND 
     Advances in semiconductor processing and logic design have permitted an increase in the amount of logic that may be present on integrated circuit devices. As a result, computer system configurations have evolved from a single or multiple integrated circuits in a system to multiple hardware threads, multiple cores, multiple devices, and/or complete systems on individual integrated circuits. Additionally, as the density of integrated circuits has grown, the power requirements for computing systems (from embedded systems to servers) have also escalated. Furthermore, software inefficiencies, and its requirements of hardware, have also caused an increase in computing device energy consumption. In fact, some studies indicate that computing devices consume a sizeable percentage of the entire electricity supply for a country, such as the United States of America. As a result, there is a vital need for energy efficiency and conservation associated with integrated circuits. These needs will increase as servers, desktop computers, notebooks, Ultrabooks™, tablets, mobile phones, processors, embedded systems, etc. become even more prevalent (from inclusion in the typical computer, automobiles, and televisions to biotechnology). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a portion of a system in accordance with an embodiment of the present invention. 
         FIG. 2  is a block diagram of a processor in accordance with an embodiment of the present invention. 
         FIG. 3  is a block diagram of a multi-domain processor in accordance with another embodiment of the present invention. 
         FIG. 4  is an embodiment of a processor including multiple cores. 
         FIG. 5  is a block diagram of a micro-architecture of a processor core in accordance with one embodiment of the present invention. 
         FIG. 6  is a block diagram of a micro-architecture of a processor core in accordance with another embodiment. 
         FIG. 7  is a block diagram of a micro-architecture of a processor core in accordance with yet another embodiment. 
         FIG. 8  is a block diagram of a micro-architecture of a processor core in accordance with a still further embodiment. 
         FIG. 9  is a block diagram of a processor in accordance with another embodiment of the present invention. 
         FIG. 10  is a block diagram of a representative SoC in accordance with an embodiment of the present invention. 
         FIG. 11  is a block diagram of another example SoC in accordance with an embodiment of the present invention. 
         FIG. 12  is a block diagram of an example system with which embodiments can be used. 
         FIG. 13  is a block diagram of another example system with which embodiments may be used. 
         FIG. 14  is a block diagram of a representative computer system. 
         FIG. 15  is a block diagram of a system in accordance with an embodiment of the present invention. 
         FIG. 16  is a block diagram of a power control logic in accordance with an embodiment of the present invention. 
         FIG. 17  is a block diagram of a processor including a hardware power control logic in accordance with another embodiment of the present invention. 
         FIG. 18  is a flow diagram of a method for controlling power consumption of a processor in accordance with an embodiment of the present invention. 
         FIG. 19  is a flow diagram of a method for controlling power consumption of a processor in accordance with another embodiment of the present invention. 
         FIG. 20  is a flow diagram of a method for updating trained model parameters in accordance with an embodiment of the present invention. 
         FIG. 21  is a state diagram of a migration logic in accordance with an embodiment of the present invention. 
         FIG. 22  is a block diagram of a memory-biased core in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In various embodiments, an intelligent multi-core power management controller for a processor is provided that learns workload characteristics on-the-fly and dynamically adjusts power configurations to provide optimal performance per energy. In one embodiment, such power configurations include the number of active cores and threads, as well as an optimal voltage and frequency for each active core. In various embodiments, a machine learning-based performance and energy model identifies particular workload behaviors such as intensive memory accesses and predicts optimal power control, including placing one or more cores into an idle or low power state while saturating memory resources. 
     In an embodiment, a power management controller is configured with a policy that determines an optimal power configuration and a mechanism to apply the decided configuration to the underlying system. Such policies may include heuristics developed by experts, and/or offline/online machine learning schemes, and may further include a number of user-level and operating system (OS)-level core-to-thread management mechanisms. 
     A power management controller as described herein may be configured to allocate only needed resources to a workload, so that performance and energy efficiency can be maximized. As an example, memory bound workloads saturate memory resources (such as bandwidth or queues) before all compute resources are fully utilized. If such workloads are executed with all threads and cores active, poor efficiency will result. Some compute bound workloads also suffer from compromised scalability due to various reasons such as increased synchronization overhead. Embodiments apply to equally to other workloads that create slack in a core, such that the core becomes underutilized. Other example workloads include I/O or network bounded workloads. Embodiments may thus identify a best power configuration for different workloads. For example, particular workloads may be identified and underutilized resources for the workloads can be powered off or operate at reduced consumption levels to enable significant energy savings without adversely affecting performance. 
     In an embodiment, the best power configuration for a workload defines the optimal number of threads and cores, execution units, voltages and frequencies, and so forth. This power configuration depends on many parameters, including both runtime workload behaviors and system power status. In addition, when considering the overheads incurred during transitions between power states, the selection process becomes even more complex. A single, fixed control policy is hard to adapt to various workloads and different systems. Embodiments thus provide a set of different models to evaluate, and an intelligent selector chooses from the identified models. This enables multiple control policies and a flexible selection at runtime. Thus embodiments may be used to determine an optimal power configuration (e.g., number of cores/threads, and voltage/frequency) concurrently for each workload, rather than a predefined control policy based on a single performance/energy prediction model. 
     Embodiments operate to save energy without adversely affecting performance for memory-intensive workloads, which saturate memory resources before fully utilizing compute resources, which can waste energy in a multicore processor. Embodiments may identify such behaviors and turn off underutilized cores to provide energy savings without a performance sacrifice. 
     In some embodiments, a heterogeneous multiprocessor may include two different types of cores: one core type optimized for computation and another core type optimized for memory accesses. In one example, both types of cores implement the same instruction set architecture (ISA) but have different microarchitectures, which may facilitate thread migration between the core types. 
     Compute and memory bounded phases of a program may have very different processor requirements that cannot be optimized by a single core type. For example, a homogeneous multiprocessor optimized for compute workloads may target for a highest core count running at a frequency that can sustain one fused multiply add (FMA) per cycle per core. However, this multiprocessor may not be very energy efficient during a program phase that is mostly waiting for memory return. This is so, as during memory bounded phases, the cores are mostly idle waiting for memory accesses, yet the idle time may not be long enough to warrant placing the core into a low power state. As a result, the idling core at a high frequency can consume unnecessary power. 
     As such, embodiments provide a heterogeneous multiprocessor that includes two or more specialized core types that are optimized for different operating points. In the examples described herein, two core types, a compute-optimized core (also referred to as a compute-biased core) and a memory-optimized core (also referred to as a memory-biased core) are provided. However understand the scope of the present invention is not limited to 2 core types, and in other cases additional core types optimized for other workload types may be present. 
     Although the following embodiments are described with reference to energy conservation and energy efficiency in specific integrated circuits, such as in computing platforms or processors, other embodiments are applicable to other types of integrated circuits and logic devices. Similar techniques and teachings of embodiments described herein may be applied to other types of circuits or semiconductor devices that may also benefit from better energy efficiency and energy conservation. For example, the disclosed embodiments are not limited to any particular type of computer systems. That is, disclosed embodiments can be used in many different system types, ranging from server computers (e.g., tower, rack, blade, micro-server and so forth), communications systems, storage systems, desktop computers of any configuration, laptop, notebook, and tablet computers (including 2:1 tablets, phablets and so forth), and may be also used in other devices, such as handheld devices, systems on chip (SoCs), and embedded applications. Some examples of handheld devices include cellular phones such as smartphones, Internet protocol devices, digital cameras, personal digital assistants (PDAs), and handheld PCs. Embedded applications may typically include a microcontroller, a digital signal processor (DSP), network computers (NetPC), set-top boxes, network hubs, wide area network (WAN) switches, wearable devices, or any other system that can perform the functions and operations taught below. More so, embodiments may be implemented in mobile terminals having standard voice functionality such as mobile phones, smartphones and phablets, and/or in non-mobile terminals without a standard wireless voice function communication capability, such as many wearables, tablets, notebooks, desktops, micro-servers, servers and so forth. Moreover, the apparatuses, methods, and systems described herein are not limited to physical computing devices, but may also relate to software optimizations for energy conservation and efficiency. As will become readily apparent in the description below, the embodiments of methods, apparatuses, and systems described herein (whether in reference to hardware, firmware, software, or a combination thereof) are vital to a ‘green technology’ future, such as for power conservation and energy efficiency in products that encompass a large portion of the US economy. 
     Referring now to  FIG. 1 , shown is a block diagram of a portion of a system in accordance with an embodiment of the present invention. As shown in  FIG. 1 , system  100  may include various components, including a processor  110  which as shown is a multicore processor. Processor  110  may be coupled to a power supply  150  via an external voltage regulator  160 , which may perform a first voltage conversion to provide a primary regulated voltage to processor  110 . 
     As seen, processor  110  may be a single die processor including multiple cores  120   a - 120   n . In addition, each core may be associated with an integrated voltage regulator (IVR)  125   a - 125   n  which receives the primary regulated voltage and generates an operating voltage to be provided to one or more agents of the processor associated with the IVR. Accordingly, an IVR implementation may be provided to allow for fine-grained control of voltage and thus power and performance of each individual core. As such, each core can operate at an independent voltage and frequency, enabling great flexibility and affording wide opportunities for balancing power consumption with performance. In some embodiments, the use of multiple IVRs enables the grouping of components into separate power planes, such that power is regulated and supplied by the IVR to only those components in the group. During power management, a given power plane of one IVR may be powered down or off when the processor is placed into a certain low power state, while another power plane of another IVR remains active, or fully powered. 
     Still referring to  FIG. 1 , additional components may be present within the processor including an input/output interface  132 , another interface  134 , and an integrated memory controller  136 . As seen, each of these components may be powered by another integrated voltage regulator  125   x . In one embodiment, interface  132  may be enable operation for an Intel® Quick Path Interconnect (QPI) interconnect, which provides for point-to-point (PtP) links in a cache coherent protocol that includes multiple layers including a physical layer, a link layer and a protocol layer. In turn, interface  134  may communicate via a Peripheral Component Interconnect Express (PCIe™) protocol. 
     Also shown is a power control unit (PCU)  138 , which may include hardware, software and/or firmware to perform power management operations with regard to processor  110 . As seen, PCU  138  provides control information to external voltage regulator  160  via a digital interface to cause the voltage regulator to generate the appropriate regulated voltage. PCU  138  also provides control information to IVRs  125  via another digital interface to control the operating voltage generated (or to cause a corresponding IVR to be disabled in a low power mode). In various embodiments, PCU  138  may include a variety of power management logic units to perform hardware-based power management. Such power management may be wholly processor controlled (e.g., by various processor hardware, and which may be triggered by workload and/or power, thermal or other processor constraints) and/or the power management may be performed responsive to external sources (such as a platform or management power management source or system software). As described further herein, PCU  138  may include control logic to perform a workload classification based on a type of workload being executed, and cause the workload to be executed on a potentially different number of cores (and at potentially different performance states) based at least in part on the workload type. 
     While not shown for ease of illustration, understand that additional components may be present within processor  110  such as uncore logic, and other components such as internal memories, e.g., one or more levels of a cache memory hierarchy and so forth. Furthermore, while shown in the implementation of  FIG. 1  with an integrated voltage regulator, embodiments are not so limited. 
     Note that the power management techniques described herein may be independent of and complementary to an operating system (OS)-based power management (OSPM) mechanism. According to one example OSPM technique, a processor can operate at various performance states or levels, so-called P-states, namely from P0 to PN. In general, the P1 performance state may correspond to the highest guaranteed performance state that can be requested by an OS. In addition to this P1 state, the OS can further request a higher performance state, namely a P0 state. This P0 state may thus be an opportunistic or turbo mode state in which, when power and/or thermal budget is available, processor hardware can configure the processor or at least portions thereof to operate at a higher than guaranteed frequency. In many implementations a processor can include multiple so-called bin frequencies above the P1 guaranteed maximum frequency, exceeding to a maximum peak frequency of the particular processor, as fused or otherwise written into the processor during manufacture. In addition, according to one OSPM mechanism, a processor can operate at various power states or levels. With regard to power states, an OSPM mechanism may specify different power consumption states, generally referred to as C-states, C0, C1 to Cn states. When a core is active, it runs at a C0 state, and when the core is idle it may be placed in a core low power state, also called a core non-zero C-state (e.g., C1-C6 states), with each C-state being at a lower power consumption level (such that C6 is a deeper low power state than C1, and so forth). 
     Understand that many different types of power management techniques may be used individually or in combination in different embodiments. As representative examples, a power controller may control the processor to be power managed by some form of dynamic voltage frequency scaling (DVFS) in which an operating voltage and/or operating frequency of one or more cores or other processor logic may be dynamically controlled to reduce power consumption in certain situations. In an example, DVFS may be performed using Enhanced Intel SpeedStep™ technology available from Intel Corporation, Santa Clara, Calif., to provide optimal performance at a lowest power consumption level. In another example, DVFS may be performed using Intel TurboBoost™ technology to enable one or more cores or other compute engines to operate at a higher than guaranteed operating frequency based on conditions (e.g., workload and availability). 
     Another power management technique that may be used in certain examples is dynamic swapping of workloads between different compute engines. For example, the processor may include asymmetric cores or other processing engines that operate at different power consumption levels, such that in a power constrained situation, one or more workloads can be dynamically switched to execute on a lower power core or other compute engine. Another exemplary power management technique is hardware duty cycling (HDC), which may cause cores and/or other compute engines to be periodically enabled and disabled according to a duty cycle, such that one or more cores may be made inactive during an inactive period of the duty cycle and made active during an active period of the duty cycle. Although described with these particular examples, understand that many other power management techniques may be used in particular embodiments. 
     Embodiments can be implemented in processors for various markets including server processors, desktop processors, mobile processors and so forth. Referring now to  FIG. 2 , shown is a block diagram of a processor in accordance with an embodiment of the present invention. As shown in  FIG. 2 , processor  200  may be a multicore processor including a plurality of cores  210   a - 210   n . In one embodiment, each such core may be of an independent power domain and can be configured to enter and exit active states and/or maximum performance states based on workload. The various cores may be coupled via an interconnect  215  to a system agent or uncore  220  that includes various components. As seen, the uncore  220  may include a shared cache  230  which may be a last level cache. In addition, the uncore may include an integrated memory controller  240  to communicate with a system memory (not shown in  FIG. 2 ), e.g., via a memory bus. Uncore  220  also includes various interfaces  250  and a power control unit  255 , which may include a workload classification logic  256  (that may include or be associated with machine learning logic) to classify a workload being executed and perform dynamic control of a number of cores and/or performance state based at least in part thereon, as described herein. 
     In addition, by interfaces  250   a - 250   n , connection can be made to various off-chip components such as peripheral devices, mass storage and so forth. While shown with this particular implementation in the embodiment of  FIG. 2 , the scope of the present invention is not limited in this regard. 
     Referring now to  FIG. 3 , shown is a block diagram of a multi-domain processor in accordance with another embodiment of the present invention. As shown in the embodiment of  FIG. 3 , processor  300  includes multiple domains. Specifically, a core domain  310  can include a plurality of cores  310   0 - 310   n , a graphics domain  320  can include one or more graphics engines, and a system agent domain  350  may further be present. In some embodiments, system agent domain  350  may execute at an independent frequency than the core domain and may remain powered on at all times to handle power control events and power management such that domains  310  and  320  can be controlled to dynamically enter into and exit high power and low power states. Each of domains  310  and  320  may operate at different voltage and/or power. Note that while only shown with three domains, understand the scope of the present invention is not limited in this regard and additional domains can be present in other embodiments. For example, multiple core domains may be present each including at least one core. 
     In general, each core  310  may further include low level caches in addition to various execution units and additional processing elements. In turn, the various cores may be coupled to each other and to a shared cache memory formed of a plurality of units of a last level cache (LLC)  340   0 - 340   n . In various embodiments, LLC  340  may be shared amongst the cores and the graphics engine, as well as various media processing circuitry. As seen, a ring interconnect  330  thus couples the cores together, and provides interconnection between the cores, graphics domain  320  and system agent circuitry  350 . In one embodiment, interconnect  330  can be part of the core domain. However in other embodiments the ring interconnect can be of its own domain. 
     As further seen, system agent domain  350  may include display controller  352  which may provide control of and an interface to an associated display. As further seen, system agent domain  350  may include a power control unit  355  which can include a workload classification logic  356  (itself including machine learning logic) to perform the workload classification-based thread migration and power control techniques as described herein. 
     As further seen in  FIG. 3 , processor  300  can further include an integrated memory controller (IMC)  370  that can provide for an interface to a system memory, such as a dynamic random access memory (DRAM). Multiple interfaces  380   0 - 380   n  may be present to enable interconnection between the processor and other circuitry. For example, in one embodiment at least one direct media interface (DMI) interface may be provided as well as one or more PCIe™ interfaces. Still further, to provide for communications between other agents such as additional processors or other circuitry, one or more QPI interfaces may also be provided. Although shown at this high level in the embodiment of  FIG. 3 , understand the scope of the present invention is not limited in this regard. 
     Referring to  FIG. 4 , an embodiment of a processor including multiple cores is illustrated. Processor  400  includes any processor or processing device, such as a microprocessor, an embedded processor, a digital signal processor (DSP), a network processor, a handheld processor, an application processor, a co-processor, a system on a chip (SoC), or other device to execute code. Processor  400 , in one embodiment, includes at least two cores—cores  401  and  402 , which may include asymmetric cores or symmetric cores (the illustrated embodiment). However, processor  400  may include any number of processing elements that may be symmetric or asymmetric. 
     In one embodiment, a processing element refers to hardware or logic to support a software thread. Examples of hardware processing elements include: a thread unit, a thread slot, a thread, a process unit, a context, a context unit, a logical processor, a hardware thread, a core, and/or any other element, which is capable of holding a state for a processor, such as an execution state or architectural state. In other words, a processing element, in one embodiment, refers to any hardware capable of being independently associated with code, such as a software thread, operating system, application, or other code. A physical processor typically refers to an integrated circuit, which potentially includes any number of other processing elements, such as cores or hardware threads. 
     A core often refers to logic located on an integrated circuit capable of maintaining an independent architectural state, wherein each independently maintained architectural state is associated with at least some dedicated execution resources. In contrast to cores, a hardware thread typically refers to any logic located on an integrated circuit capable of maintaining an independent architectural state, wherein the independently maintained architectural states share access to execution resources. As can be seen, when certain resources are shared and others are dedicated to an architectural state, the line between the nomenclature of a hardware thread and core overlaps. Yet often, a core and a hardware thread are viewed by an operating system as individual logical processors, where the operating system is able to individually schedule operations on each logical processor. 
     Physical processor  400 , as illustrated in  FIG. 4 , includes two cores, cores  401  and  402 . Here, cores  401  and  402  are considered symmetric cores, i.e., cores with the same configurations, functional units, and/or logic. In another embodiment, core  401  includes an out-of-order processor core, while core  402  includes an in-order processor core. However, cores  401  and  402  may be individually selected from any type of core, such as a native core, a software managed core, a core adapted to execute a native instruction set architecture (ISA), a core adapted to execute a translated ISA, a co-designed core, or other known core. Yet to further the discussion, the functional units illustrated in core  401  are described in further detail below, as the units in core  402  operate in a similar manner. 
     As depicted, core  401  includes two hardware threads  401   a  and  401   b , which may also be referred to as hardware thread slots  401   a  and  401   b . Therefore, software entities, such as an operating system, in one embodiment potentially view processor  400  as four separate processors, i.e., four logical processors or processing elements capable of executing four software threads concurrently. As alluded to above, a first thread is associated with architecture state registers  401   a , a second thread is associated with architecture state registers  401   b , a third thread may be associated with architecture state registers  402   a , and a fourth thread may be associated with architecture state registers  402   b . Here, each of the architecture state registers ( 401   a ,  401   b ,  402   a , and  402   b ) may be referred to as processing elements, thread slots, or thread units, as described above. As illustrated, architecture state registers  401   a  are replicated in architecture state registers  401   b , so individual architecture states/contexts are capable of being stored for logical processor  401   a  and logical processor  401   b . In core  401 , other smaller resources, such as instruction pointers and renaming logic in allocator and renamer block  430  may also be replicated for threads  401   a  and  401   b . Some resources, such as re-order buffers in reorder/retirement unit  435 , ILTB  420 , load/store buffers, and queues may be shared through partitioning. Other resources, such as general purpose internal registers, page-table base register(s), low-level data-cache and data-TLB  415 , execution unit(s)  440 , and portions of out-of-order unit  435  are potentially fully shared. 
     Processor  400  often includes other resources, which may be fully shared, shared through partitioning, or dedicated by/to processing elements. In  FIG. 4 , an embodiment of a purely exemplary processor with illustrative logical units/resources of a processor is illustrated. Note that a processor may include, or omit, any of these functional units, as well as include any other known functional units, logic, or firmware not depicted. As illustrated, core  401  includes a simplified, representative out-of-order (OOO) processor core. But an in-order processor may be utilized in different embodiments. The OOO core includes a branch target buffer  420  to predict branches to be executed/taken and an instruction-translation buffer (I-TLB)  420  to store address translation entries for instructions. 
     Core  401  further includes decode module  425  coupled to fetch unit  420  to decode fetched elements. Fetch logic, in one embodiment, includes individual sequencers associated with thread slots  401   a ,  401   b , respectively. Usually core  401  is associated with a first ISA, which defines/specifies instructions executable on processor  400 . Often machine code instructions that are part of the first ISA include a portion of the instruction (referred to as an opcode), which references/specifies an instruction or operation to be performed. Decode logic  425  includes circuitry that recognizes these instructions from their opcodes and passes the decoded instructions on in the pipeline for processing as defined by the first ISA. For example, decoders  425 , in one embodiment, include logic designed or adapted to recognize specific instructions, such as transactional instruction. As a result of the recognition by decoders  425 , the architecture or core  401  takes specific, predefined actions to perform tasks associated with the appropriate instruction. It is important to note that any of the tasks, blocks, operations, and methods described herein may be performed in response to a single or multiple instructions; some of which may be new or old instructions. 
     In one example, allocator and renamer block  430  includes an allocator to reserve resources, such as register files to store instruction processing results. However, threads  401   a  and  401   b  are potentially capable of out-of-order execution, where allocator and renamer block  430  also reserves other resources, such as reorder buffers to track instruction results. Unit  430  may also include a register renamer to rename program/instruction reference registers to other registers internal to processor  400 . Reorder/retirement unit  435  includes components, such as the reorder buffers mentioned above, load buffers, and store buffers, to support out-of-order execution and later in-order retirement of instructions executed out-of-order. 
     Scheduler and execution unit(s) block  440 , in one embodiment, includes a scheduler unit to schedule instructions/operation on execution units. For example, a floating point instruction is scheduled on a port of an execution unit that has an available floating point execution unit. Register files associated with the execution units are also included to store information instruction processing results. Exemplary execution units include a floating point execution unit, an integer execution unit, a jump execution unit, a load execution unit, a store execution unit, and other known execution units. 
     Lower level data cache and data translation buffer (D-TLB)  450  are coupled to execution unit(s)  440 . The data cache is to store recently used/operated on elements, such as data operands, which are potentially held in memory coherency states. The D-TLB is to store recent virtual/linear to physical address translations. As a specific example, a processor may include a page table structure to break physical memory into a plurality of virtual pages. 
     Here, cores  401  and  402  share access to higher-level or further-out cache  410 , which is to cache recently fetched elements. Note that higher-level or further-out refers to cache levels increasing or getting further away from the execution unit(s). In one embodiment, higher-level cache  410  is a last-level data cache—last cache in the memory hierarchy on processor  400 —such as a second or third level data cache. However, higher level cache  410  is not so limited, as it may be associated with or includes an instruction cache. A trace cache—a type of instruction cache-instead may be coupled after decoder  425  to store recently decoded traces. 
     In the depicted configuration, processor  400  also includes bus interface module  405  and a power controller  460 , which may perform power management in accordance with an embodiment of the present invention. In this scenario, bus interface  405  is to communicate with devices external to processor  400 , such as system memory and other components. 
     A memory controller  470  may interface with other devices such as one or many memories. In an example, bus interface  405  includes a ring interconnect with a memory controller for interfacing with a memory and a graphics controller for interfacing with a graphics processor. In an SoC environment, even more devices, such as a network interface, coprocessors, memory, graphics processor, and any other known computer devices/interface may be integrated on a single die or integrated circuit to provide small form factor with high functionality and low power consumption. 
     Referring now to  FIG. 5 , shown is a block diagram of a micro-architecture of a processor core in accordance with one embodiment of the present invention. As shown in  FIG. 5 , processor core  500  may be a multi-stage pipelined out-of-order processor. Core  500  may operate at various voltages based on a received operating voltage, which may be received from an integrated voltage regulator or external voltage regulator. 
     As seen in  FIG. 5 , core  500  includes front end units  510 , which may be used to fetch instructions to be executed and prepare them for use later in the processor pipeline. For example, front end units  510  may include a fetch unit  501 , an instruction cache  503 , and an instruction decoder  505 . In some implementations, front end units  510  may further include a trace cache, along with microcode storage as well as a micro-operation storage. Fetch unit  501  may fetch macro-instructions, e.g., from memory or instruction cache  503 , and feed them to instruction decoder  505  to decode them into primitives, i.e., micro-operations for execution by the processor. 
     Coupled between front end units  510  and execution units  520  is an out-of-order (OOO) engine  515  that may be used to receive the micro-instructions and prepare them for execution. More specifically OOO engine  515  may include various buffers to re-order micro-instruction flow and allocate various resources needed for execution, as well as to provide renaming of logical registers onto storage locations within various register files such as register file  530  and extended register file  535 . Register file  530  may include separate register files for integer and floating point operations. For purposes of configuration, control, and additional operations, a set of machine specific registers (MSRs)  538  may also be present and accessible to various logic within core  500  (and external to the core). For example, power limit information may be stored in one or more MSR and be dynamically updated as described herein. 
     Various resources may be present in execution units  520 , including, for example, various integer, floating point, and single instruction multiple data (SIMD) logic units, among other specialized hardware. For example, such execution units may include one or more arithmetic logic units (ALUs)  522  and one or more vector execution units  524 , among other such execution units. 
     Results from the execution units may be provided to retirement logic, namely a reorder buffer (ROB)  540 . More specifically, ROB  540  may include various arrays and logic to receive information associated with instructions that are executed. This information is then examined by ROB  540  to determine whether the instructions can be validly retired and result data committed to the architectural state of the processor, or whether one or more exceptions occurred that prevent a proper retirement of the instructions. Of course, ROB  540  may handle other operations associated with retirement. 
     As shown in  FIG. 5 , ROB  540  is coupled to a cache  550  which, in one embodiment may be a low level cache (e.g., an L1 cache) although the scope of the present invention is not limited in this regard. Also, execution units  520  can be directly coupled to cache  550 . From cache  550 , data communication may occur with higher level caches, system memory and so forth. While shown with this high level in the embodiment of  FIG. 5 , understand the scope of the present invention is not limited in this regard. For example, while the implementation of  FIG. 5  is with regard to an out-of-order machine such as of an Intel® x86 instruction set architecture (ISA), the scope of the present invention is not limited in this regard. That is, other embodiments may be implemented in an in-order processor, a reduced instruction set computing (RISC) processor such as an ARM-based processor, or a processor of another type of ISA that can emulate instructions and operations of a different ISA via an emulation engine and associated logic circuitry. 
     Referring now to  FIG. 6 , shown is a block diagram of a micro-architecture of a processor core in accordance with another embodiment. In the embodiment of  FIG. 6 , core  600  may be a low power core of a different micro-architecture, such as an Intel® Atom™-based processor having a relatively limited pipeline depth designed to reduce power consumption. As seen, core  600  includes an instruction cache  610  coupled to provide instructions to an instruction decoder  615 . A branch predictor  605  may be coupled to instruction cache  610 . Note that instruction cache  610  may further be coupled to another level of a cache memory, such as an L2 cache (not shown for ease of illustration in  FIG. 6 ). In turn, instruction decoder  615  provides decoded instructions to an issue queue  620  for storage and delivery to a given execution pipeline. A microcode ROM  618  is coupled to instruction decoder  615 . 
     A floating point pipeline  630  includes a floating point register file  632  which may include a plurality of architectural registers of a given bit with such as 128, 256 or 512 bits. Pipeline  630  includes a floating point scheduler  634  to schedule instructions for execution on one of multiple execution units of the pipeline. In the embodiment shown, such execution units include an ALU  635 , a shuffle unit  636 , and a floating point adder  638 . In turn, results generated in these execution units may be provided back to buffers and/or registers of register file  632 . Of course understand while shown with these few example execution units, additional or different floating point execution units may be present in another embodiment. 
     An integer pipeline  640  also may be provided. In the embodiment shown, pipeline  640  includes an integer register file  642  which may include a plurality of architectural registers of a given bit with such as 128 or 256 bits. Pipeline  640  includes an integer scheduler  644  to schedule instructions for execution on one of multiple execution units of the pipeline. In the embodiment shown, such execution units include an ALU  645 , a shifter unit  646 , and a jump execution unit  648 . In turn, results generated in these execution units may be provided back to buffers and/or registers of register file  642 . Of course understand while shown with these few example execution units, additional or different integer execution units may be present in another embodiment. 
     A memory execution scheduler  650  may schedule memory operations for execution in an address generation unit  652 , which is also coupled to a TLB  654 . As seen, these structures may couple to a data cache  660 , which may be a L0 and/or L1 data cache that in turn couples to additional levels of a cache memory hierarchy, including an L2 cache memory. 
     To provide support for out-of-order execution, an allocator/renamer  670  may be provided, in addition to a reorder buffer  680 , which is configured to reorder instructions executed out of order for retirement in order. Although shown with this particular pipeline architecture in the illustration of  FIG. 6 , understand that many variations and alternatives are possible. 
     Note that in a processor having asymmetric cores, such as in accordance with the micro-architectures of  FIGS. 5 and 6 , workloads may be dynamically swapped between the cores for power management reasons, as these cores, although having different pipeline designs and depths, may be of the same or related ISA. Such dynamic core swapping may be performed in a manner transparent to a user application (and possibly kernel also). 
     Referring to  FIG. 7 , shown is a block diagram of a micro-architecture of a processor core in accordance with yet another embodiment. As illustrated in  FIG. 7 , a core  700  may include a multi-staged in-order pipeline to execute at very low power consumption levels. As one such example, processor  700  may have a micro-architecture in accordance with an ARM Cortex A53 design available from ARM Holdings, LTD., Sunnyvale, Calif. In an implementation, an 8-stage pipeline may be provided that is configured to execute both 32-bit and 64-bit code. Core  700  includes a fetch unit  710  that is configured to fetch instructions and provide them to a decode unit  715 , which may decode the instructions, e.g., macro-instructions of a given ISA such as an ARMv8 ISA. Note further that a queue  730  may couple to decode unit  715  to store decoded instructions. Decoded instructions are provided to an issue logic  725 , where the decoded instructions may be issued to a given one of multiple execution units. 
     With further reference to  FIG. 7 , issue logic  725  may issue instructions to one of multiple execution units. In the embodiment shown, these execution units include an integer unit  735 , a multiply unit  740 , a floating point/vector unit  750 , a dual issue unit  760 , and a load/store unit  770 . The results of these different execution units may be provided to a writeback unit  780 . Understand that while a single writeback unit is shown for ease of illustration, in some implementations separate writeback units may be associated with each of the execution units. Furthermore, understand that while each of the units and logic shown in  FIG. 7  is represented at a high level, a particular implementation may include more or different structures. A processor designed using one or more cores having a pipeline as in  FIG. 7  may be implemented in many different end products, extending from mobile devices to server systems. 
     Referring to  FIG. 8 , shown is a block diagram of a micro-architecture of a processor core in accordance with a still further embodiment. As illustrated in  FIG. 8 , a core  800  may include a multi-stage multi-issue out-of-order pipeline to execute at very high performance levels (which may occur at higher power consumption levels than core  700  of  FIG. 7 ). As one such example, processor  800  may have a microarchitecture in accordance with an ARM Cortex A57 design. In an implementation, a 15 (or greater)-stage pipeline may be provided that is configured to execute both 32-bit and 64-bit code. In addition, the pipeline may provide for 3 (or greater)-wide and 3 (or greater)-issue operation. Core  800  includes a fetch unit  810  that is configured to fetch instructions and provide them to a decoder/renamer/dispatcher  815 , which may decode the instructions, e.g., macro-instructions of an ARMv8 instruction set architecture, rename register references within the instructions, and dispatch the instructions (eventually) to a selected execution unit. Decoded instructions may be stored in a queue  825 . Note that while a single queue structure is shown for ease of illustration in  FIG. 8 , understand that separate queues may be provided for each of the multiple different types of execution units. 
     Also shown in  FIG. 8  is an issue logic  830  from which decoded instructions stored in queue  825  may be issued to a selected execution unit. Issue logic  830  also may be implemented in a particular embodiment with a separate issue logic for each of the multiple different types of execution units to which issue logic  830  couples. 
     Decoded instructions may be issued to a given one of multiple execution units. In the embodiment shown, these execution units include one or more integer units  835 , a multiply unit  840 , a floating point/vector unit  850 , a branch unit  860 , and a load/store unit  870 . In an embodiment, floating point/vector unit  850  may be configured to handle SIMD or vector data of 128 or 256 bits. Still further, floating point/vector execution unit  850  may perform IEEE-754 double precision floating-point operations. The results of these different execution units may be provided to a writeback unit  880 . Note that in some implementations separate writeback units may be associated with each of the execution units. Furthermore, understand that while each of the units and logic shown in  FIG. 8  is represented at a high level, a particular implementation may include more or different structures. 
     Note that in a processor having asymmetric cores, such as in accordance with the micro-architectures of  FIGS. 7 and 8 , workloads may be dynamically swapped for power management reasons, as these cores, although having different pipeline designs and depths, may be of the same or related ISA. Such dynamic core swapping may be performed in a manner transparent to a user application (and possibly kernel also). 
     A processor designed using one or more cores having pipelines as in any one or more of  FIGS. 5-8  may be implemented in many different end products, extending from mobile devices to server systems. Referring now to  FIG. 9 , shown is a block diagram of a processor in accordance with another embodiment of the present invention. In the embodiment of  FIG. 9 , processor  900  may be a SoC including multiple domains, each of which may be controlled to operate at an independent operating voltage and operating frequency. As a specific illustrative example, processor  900  may be an Intel® Architecture Core™-based processor such as an i3, i5, i7 or another such processor available from Intel Corporation. However, other low power processors such as available from Advanced Micro Devices, Inc. (AMD) of Sunnyvale, Calif., an ARM-based design from ARM Holdings, Ltd. or licensee thereof or a MIPS-based design from MIPS Technologies, Inc. of Sunnyvale, Calif., or their licensees or adopters may instead be present in other embodiments such as an Apple A7 processor, a Qualcomm Snapdragon processor, or Texas Instruments OMAP processor. Such SoC may be used in a low power system such as a smartphone, tablet computer, phablet computer, Ultrabook™ computer or other portable computing device. 
     In the high level view shown in  FIG. 9 , processor  900  includes a plurality of core units  910   0 - 910   n . Each core unit may include one or more processor cores, one or more cache memories and other circuitry. Each core unit  910  may support one or more instructions sets (e.g., an x86 instruction set (with some extensions that have been added with newer versions); a MIPS instruction set; an ARM instruction set (with optional additional extensions such as NEON)) or other instruction set or combinations thereof. Note that some of the core units may be heterogeneous resources (e.g., of a different design). In addition, each such core may be coupled to a cache memory (not shown) which in an embodiment may be a shared level (L2) cache memory. A non-volatile storage  930  may be used to store various program and other data. For example, this storage may be used to store at least portions of microcode, boot information such as a BIOS, other system software or so forth. 
     Each core unit  910  may also include an interface such as a bus interface unit to enable interconnection to additional circuitry of the processor. In an embodiment, each core unit  910  couples to a coherent fabric that may act as a primary cache coherent on-die interconnect that in turn couples to a memory controller  935 . In turn, memory controller  935  controls communications with a memory such as a DRAM (not shown for ease of illustration in  FIG. 9 ). 
     In addition to core units, additional processing engines are present within the processor, including at least one graphics unit  920  which may include one or more graphics processing units (GPUs) to perform graphics processing as well as to possibly execute general purpose operations on the graphics processor (so-called GPGPU operation). In addition, at least one image signal processor  925  may be present. Signal processor  925  may be configured to process incoming image data received from one or more capture devices, either internal to the SoC or off-chip. 
     Other accelerators also may be present. In the illustration of  FIG. 9 , a video coder  950  may perform coding operations including encoding and decoding for video information, e.g., providing hardware acceleration support for high definition video content. A display controller  955  further may be provided to accelerate display operations including providing support for internal and external displays of a system. In addition, a security processor  945  may be present to perform security operations such as secure boot operations, various cryptography operations and so forth. 
     Each of the units may have its power consumption controlled via a power manager  940 , which may include control logic to perform the various power management techniques described herein. For example, power manager  940  may include a machine learning/workload classification logic to classify a workload being executed and migration logic, which may cause at least some threads of the workload to be dynamically migrated to different cores (and/or core types), such that a different number of cores may be active in a next operating interval. 
     In some embodiments, SoC  900  may further include a non-coherent fabric coupled to the coherent fabric to which various peripheral devices may couple. One or more interfaces  960   a - 960   d  enable communication with one or more off-chip devices. Such communications may be via a variety of communication protocols such as PCIe™, GPIO, USB, I 2 C, UART, MIPI, SDIO, DDR, SPI, HDMI, among other types of communication protocols. Although shown at this high level in the embodiment of  FIG. 9 , understand the scope of the present invention is not limited in this regard. 
     Referring now to  FIG. 10 , shown is a block diagram of a representative SoC. In the embodiment shown, SoC  1000  may be a multi-core SoC configured for low power operation to be optimized for incorporation into a smartphone or other low power device such as a tablet computer or other portable computing device. As an example, SoC  1000  may be implemented using asymmetric or different types of cores, such as combinations of higher power and/or low power cores, e.g., out-of-order cores and in-order cores. In different embodiments, these cores may be based on an Intel® Architecture™ core design or an ARM architecture design. In yet other embodiments, a mix of Intel and ARM cores may be implemented in a given SoC. 
     As seen in  FIG. 10 , SoC  1000  includes a first core domain  1010  having a plurality of first cores  1012   0 - 1012   3 . In an example, these cores may be low power cores such as in-order cores. In one embodiment these first cores may be implemented as ARM Cortex A53 cores. In turn, these cores couple to a cache memory  1015  of core domain  1010 . In addition, SoC  1000  includes a second core domain  1020 . In the illustration of  FIG. 10 , second core domain  1020  has a plurality of second cores  1022   0 - 1022   3 . In an example, these cores may be higher power-consuming cores than first cores  1012 . In an embodiment, the second cores may be out-of-order cores, which may be implemented as ARM Cortex A57 cores. In turn, these cores couple to a cache memory  1025  of core domain  1020 . Note that while the example shown in  FIG. 10  includes 4 cores in each domain, understand that more or fewer cores may be present in a given domain in other examples. 
     With further reference to  FIG. 10 , a graphics domain  1030  also is provided, which may include one or more graphics processing units (GPUs) configured to independently execute graphics workloads, e.g., provided by one or more cores of core domains  1010  and  1020 . As an example, GPU domain  1030  may be used to provide display support for a variety of screen sizes, in addition to providing graphics and display rendering operations. 
     As seen, the various domains couple to a coherent interconnect  1040 , which in an embodiment may be a cache coherent interconnect fabric that in turn couples to an integrated memory controller  1050 . Coherent interconnect  1040  may include a shared cache memory, such as an L3 cache, in some examples. In an embodiment, memory controller  1050  may be a direct memory controller to provide for multiple channels of communication with an off-chip memory, such as multiple channels of a DRAM (not shown for ease of illustration in  FIG. 10 ). 
     In different examples, the number of the core domains may vary. For example, for a low power SoC suitable for incorporation into a mobile computing device, a limited number of core domains such as shown in  FIG. 10  may be present. Still further, in such low power SoCs, core domain  1020  including higher power cores may have fewer numbers of such cores. For example, in one implementation two cores  1022  may be provided to enable operation at reduced power consumption levels. In addition, the different core domains may also be coupled to an interrupt controller to enable dynamic swapping of workloads between the different domains. 
     In yet other embodiments, a greater number of core domains, as well as additional optional IP logic may be present, in that an SoC can be scaled to higher performance (and power) levels for incorporation into other computing devices, such as desktops, servers, high performance computing systems, base stations forth. As one such example, 4 core domains each having a given number of out-of-order cores may be provided. Still further, in addition to optional GPU support (which as an example may take the form of a GPGPU), one or more accelerators to provide optimized hardware support for particular functions (e.g. web serving, network processing, switching or so forth) also may be provided. In addition, an input/output interface may be present to couple such accelerators to off-chip components. 
     Referring now to  FIG. 11 , shown is a block diagram of another example SoC. In the embodiment of  FIG. 11 , SoC  1100  may include various circuitry to enable high performance for multimedia applications, communications and other functions. As such, SoC  1100  is suitable for incorporation into a wide variety of portable and other devices, such as smartphones, tablet computers, smart TVs and so forth. In the example shown, SoC  1100  includes a central processor unit (CPU) domain  1110 . In an embodiment, a plurality of individual processor cores may be present in CPU domain  1110 . As one example, CPU domain  1110  may be a quad core processor having 4 multithreaded cores. Such processors may be homogeneous or heterogeneous processors, e.g., a mix of low power and high power processor cores. 
     In turn, a GPU domain  1120  is provided to perform advanced graphics processing in one or more GPUs to handle graphics and compute APIs. A DSP unit  1130  may provide one or more low power DSPs for handling low-power multimedia applications such as music playback, audio/video and so forth, in addition to advanced calculations that may occur during execution of multimedia instructions. In turn, a communication unit  1140  may include various components to provide connectivity via various wireless protocols, such as cellular communications (including 3G/4G LTE), wireless local area protocols such as Bluetooth™ IEEE 802.11, and so forth. 
     Still further, a multimedia processor  1150  may be used to perform capture and playback of high definition video and audio content, including processing of user gestures. A sensor unit  1160  may include a plurality of sensors and/or a sensor controller to interface to various off-chip sensors present in a given platform. An image signal processor  1170  may be provided with one or more separate ISPs to perform image processing with regard to captured content from one or more cameras of a platform, including still and video cameras. 
     A display processor  1180  may provide support for connection to a high definition display of a given pixel density, including the ability to wirelessly communicate content for playback on such display. Still further, a location unit  1190  may include a GPS receiver with support for multiple GPS constellations to provide applications highly accurate positioning information obtained using as such GPS receiver. Understand that while shown with this particular set of components in the example of  FIG. 11 , many variations and alternatives are possible. 
     Referring now to  FIG. 12 , shown is a block diagram of an example system with which embodiments can be used. As seen, system  1200  may be a smartphone or other wireless communicator. A baseband processor  1205  is configured to perform various signal processing with regard to communication signals to be transmitted from or received by the system. In turn, baseband processor  1205  is coupled to an application processor  1210 , which may be a main CPU of the system to execute an OS and other system software, in addition to user applications such as many well-known social media and multimedia apps. Application processor  1210  may further be configured to perform a variety of other computing operations for the device. 
     In turn, application processor  1210  can couple to a user interface/display  1220 , e.g., a touch screen display. In addition, application processor  1210  may couple to a memory system including a non-volatile memory, namely a flash memory  1230  and a system memory, namely a dynamic random access memory (DRAM)  1235 . As further seen, application processor  1210  further couples to a capture device  1240  such as one or more image capture devices that can record video and/or still images. 
     Still referring to  FIG. 12 , a universal integrated circuit card (UICC)  1240  comprising a subscriber identity module and possibly a secure storage and cryptoprocessor is also coupled to application processor  1210 . System  1200  may further include a security processor  1250  that may couple to application processor  1210 . A plurality of sensors  1225  may couple to application processor  1210  to enable input of a variety of sensed information such as accelerometer and other environmental information. An audio output device  1295  may provide an interface to output sound, e.g., in the form of voice communications, played or streaming audio data and so forth. 
     As further illustrated, a near field communication (NFC) contactless interface  1260  is provided that communicates in a NFC near field via an NFC antenna  1265 . While separate antennae are shown in  FIG. 12 , understand that in some implementations one antenna or a different set of antennae may be provided to enable various wireless functionality. 
     A power management integrated circuit (PMIC)  1215  couples to application processor  1210  to perform platform level power management. To this end, PMIC  1215  may issue power management requests to application processor  1210  to enter certain low power states as desired. Furthermore, based on platform constraints, PMIC  1215  may also control the power level of other components of system  1200 . 
     To enable communications to be transmitted and received, various circuitry may be coupled between baseband processor  1205  and an antenna  1290 . Specifically, a radio frequency (RF) transceiver  1270  and a wireless local area network (WLAN) transceiver  1275  may be present. In general, RF transceiver  1270  may be used to receive and transmit wireless data and calls according to a given wireless communication protocol such as 3G or 4G wireless communication protocol such as in accordance with a code division multiple access (CDMA), global system for mobile communication (GSM), long term evolution (LTE) or other protocol. In addition a GPS sensor  1280  may be present. Other wireless communications such as receipt or transmission of radio signals, e.g., AM/FM and other signals may also be provided. In addition, via WLAN transceiver  1275 , local wireless communications can also be realized. 
     Referring now to  FIG. 13 , shown is a block diagram of another example system with which embodiments may be used. In the illustration of  FIG. 13 , system  1300  may be mobile low-power system such as a tablet computer, 2:1 tablet, phablet or other convertible or standalone tablet system. As illustrated, a SoC  1310  is present and may be configured to operate as an application processor for the device. 
     A variety of devices may couple to SoC  1310 . In the illustration shown, a memory subsystem includes a flash memory  1340  and a DRAM  1345  coupled to SoC  1310 . In addition, a touch panel  1320  is coupled to the SoC  1310  to provide display capability and user input via touch, including provision of a virtual keyboard on a display of touch panel  1320 . To provide wired network connectivity, SoC  1310  couples to an Ethernet interface  1330 . A peripheral hub  1325  is coupled to SoC  1310  to enable interfacing with various peripheral devices, such as may be coupled to system  1300  by any of various ports or other connectors. 
     In addition to internal power management circuitry and functionality within SoC  1310 , a PMIC  1380  is coupled to SoC  1310  to provide platform-based power management, e.g., based on whether the system is powered by a battery  1390  or AC power via an AC adapter  1395 . In addition to this power source-based power management, PMIC  1380  may further perform platform power management activities based on environmental and usage conditions. Still further, PMIC  1380  may communicate control and status information to SoC  1310  to cause various power management actions within SoC  1310 . 
     Still referring to  FIG. 13 , to provide for wireless capabilities, a WLAN unit  1350  is coupled to SoC  1310  and in turn to an antenna  1355 . In various implementations, WLAN unit  1350  may provide for communication according to one or more wireless protocols. 
     As further illustrated, a plurality of sensors  1360  may couple to SoC  1310 . These sensors may include various accelerometer, environmental and other sensors, including user gesture sensors. Finally, an audio codec  1365  is coupled to SoC  1310  to provide an interface to an audio output device  1370 . Of course understand that while shown with this particular implementation in  FIG. 13 , many variations and alternatives are possible. 
     Referring now to  FIG. 14 , shown is a block diagram of a representative computer system such as notebook, Ultrabook™ or other small form factor system. A processor  1410 , in one embodiment, includes a microprocessor, multi-core processor, multithreaded processor, an ultra low voltage processor, an embedded processor, or other known processing element. In the illustrated implementation, processor  1410  acts as a main processing unit and central hub for communication with many of the various components of the system  1400 . As one example, processor  1400  is implemented as a SoC. 
     Processor  1410 , in one embodiment, communicates with a system memory  1415 . As an illustrative example, the system memory  1415  is implemented via multiple memory devices or modules to provide for a given amount of system memory. 
     To provide for persistent storage of information such as data, applications, one or more operating systems and so forth, a mass storage  1420  may also couple to processor  1410 . In various embodiments, to enable a thinner and lighter system design as well as to improve system responsiveness, this mass storage may be implemented via a SSD or the mass storage may primarily be implemented using a hard disk drive (HDD) with a smaller amount of SSD storage to act as a SSD cache to enable non-volatile storage of context state and other such information during power down events so that a fast power up can occur on re-initiation of system activities. Also shown in  FIG. 14 , a flash device  1422  may be coupled to processor  1410 , e.g., via a serial peripheral interface (SPI). This flash device may provide for non-volatile storage of system software, including a basic input/output software (BIOS) as well as other firmware of the system. 
     Various input/output (I/O) devices may be present within system  1400 . Specifically shown in the embodiment of  FIG. 14  is a display  1424  which may be a high definition LCD or LED panel that further provides for a touch screen  1425 . In one embodiment, display  1424  may be coupled to processor  1410  via a display interconnect that can be implemented as a high performance graphics interconnect. Touch screen  1425  may be coupled to processor  1410  via another interconnect, which in an embodiment can be an I 2 C interconnect. As further shown in  FIG. 14 , in addition to touch screen  1425 , user input by way of touch can also occur via a touch pad  1430  which may be configured within the chassis and may also be coupled to the same I 2 C interconnect as touch screen  1425 . 
     For perceptual computing and other purposes, various sensors may be present within the system and may be coupled to processor  1410  in different manners. Certain inertial and environmental sensors may couple to processor  1410  through a sensor hub  1440 , e.g., via an I 2 C interconnect. In the embodiment shown in  FIG. 14 , these sensors may include an accelerometer  1441 , an ambient light sensor (ALS)  1442 , a compass  1443  and a gyroscope  1444 . Other environmental sensors may include one or more thermal sensors  1446  which in some embodiments couple to processor  1410  via a system management bus (SMBus) bus. 
     Also seen in  FIG. 14 , various peripheral devices may couple to processor  1410  via a low pin count (LPC) interconnect. In the embodiment shown, various components can be coupled through an embedded controller  1435 . Such components can include a keyboard  1436  (e.g., coupled via a PS2 interface), a fan  1437 , and a thermal sensor  1439 . In some embodiments, touch pad  1430  may also couple to EC  1435  via a PS2 interface. In addition, a security processor such as a trusted platform module (TPM)  1438  may also couple to processor  1410  via this LPC interconnect. 
     System  1400  can communicate with external devices in a variety of manners, including wirelessly. In the embodiment shown in  FIG. 14 , various wireless modules, each of which can correspond to a radio configured for a particular wireless communication protocol, are present. One manner for wireless communication in a short range such as a near field may be via a NFC unit  1445  which may communicate, in one embodiment with processor  1410  via an SMBus. Note that via this NFC unit  1445 , devices in close proximity to each other can communicate. 
     As further seen in  FIG. 14 , additional wireless units can include other short range wireless engines including a WLAN unit  1450  and a Bluetooth unit  1452 . Using WLAN unit  1450 , Wi-Fi™ communications can be realized, while via Bluetooth unit  1452 , short range Bluetooth™ communications can occur. These units may communicate with processor  1410  via a given link. 
     In addition, wireless wide area communications, e.g., according to a cellular or other wireless wide area protocol, can occur via a WWAN unit  1456  which in turn may couple to a subscriber identity module (SIM)  1457 . In addition, to enable receipt and use of location information, a GPS module  1455  may also be present. Note that in the embodiment shown in  FIG. 14 , WWAN unit  1456  and an integrated capture device such as a camera module  1454  may communicate via a given link. 
     An integrated camera module  1454  can be incorporated in the lid. To provide for audio inputs and outputs, an audio processor can be implemented via a digital signal processor (DSP)  1460 , which may couple to processor  1410  via a high definition audio (HDA) link. Similarly, DSP  1460  may communicate with an integrated coder/decoder (CODEC) and amplifier  1462  that in turn may couple to output speakers  1463  which may be implemented within the chassis. Similarly, amplifier and CODEC  1462  can be coupled to receive audio inputs from a microphone  1465  which in an embodiment can be implemented via dual array microphones (such as a digital microphone array) to provide for high quality audio inputs to enable voice-activated control of various operations within the system. Note also that audio outputs can be provided from amplifier/CODEC  1462  to a headphone jack  1464 . Although shown with these particular components in the embodiment of  FIG. 14 , understand the scope of the present invention is not limited in this regard. 
     Embodiments may be implemented in many different system types. Referring now to  FIG. 15 , shown is a block diagram of a system in accordance with an embodiment of the present invention. As shown in  FIG. 15 , multiprocessor system  1500  is a point-to-point interconnect system, and includes a first processor  1570  and a second processor  1580  coupled via a point-to-point interconnect  1550 . As shown in  FIG. 15 , each of processors  1570  and  1580  may be multicore processors, including first and second processor cores (i.e., processor cores  1574   a  and  1574   b  and processor cores  1584   a  and  1584   b ), although potentially many more cores may be present in the processors. Each of the processors can include a PCU or other power management logic to perform processor-based power management as described herein, including workload classification and dynamic thread migration and core performance control based at least in part thereon. 
     Still referring to  FIG. 15 , first processor  1570  further includes a memory controller hub (MCH)  1572  and point-to-point (P-P) interfaces  1576  and  1578 . Similarly, second processor  1580  includes a MCH  1582  and P-P interfaces  1586  and  1588 . As shown in  FIG. 15 , MCH&#39;s  1572  and  1582  couple the processors to respective memories, namely a memory  1532  and a memory  1534 , which may be portions of system memory (e.g., DRAM) locally attached to the respective processors. First processor  1570  and second processor  1580  may be coupled to a chipset  1590  via P-P interconnects  1562  and  1564 , respectively. As shown in  FIG. 15 , chipset  1590  includes P-P interfaces  1594  and  1598 . 
     Furthermore, chipset  1590  includes an interface  1592  to couple chipset  1590  with a high performance graphics engine  1538 , by a P-P interconnect  1539 . In turn, chipset  1590  may be coupled to a first bus  1516  via an interface  1596 . As shown in  FIG. 15 , various input/output (I/O) devices  1514  may be coupled to first bus  1516 , along with a bus bridge  1518  which couples first bus  1516  to a second bus  1520 . Various devices may be coupled to second bus  1520  including, for example, a keyboard/mouse  1522 , communication devices  1526  and a data storage unit  1528  such as a disk drive or other mass storage device which may include code  1530 , in one embodiment. Further, an audio I/O  1524  may be coupled to second bus  1520 . Embodiments can be incorporated into other types of systems including mobile devices such as a smart cellular telephone, tablet computer, netbook, Ultrabook™, or so forth. 
     In an embodiment, a prediction logic is adapted to determine an optimal power configuration, and a control logic is adapted to apply the determined power configuration. The prediction logic collects input statistics periodically by reading performance/energy counters, and then using an intelligent model to evaluate the current status and predict the next optimal power configuration. The control logic applies this power control decision to the underlying system via thread migration and dynamic voltage and frequency scaling, in an embodiment. In some embodiments, one or more heterogeneous cores may be present that are specialized for memory-intensive workloads. Threads can migrate to such core(s) to save more energy during a memory-bound phase. A hardware thread migration technique may be used to migrate threads between compute-biased cores and memory-biased cores, which does not involve any software intervention, both from user applications and operating system standpoint. 
     Because compute-bound and memory-bound workloads have very different system requirements, the model solves a classification problem. Given a set of power configuration parameters (e.g., number of cores, number of threads, clock frequency and voltage) and runtime statistics (e.g., various performance/energy counters) at a current time sample, the goal is to find the optimal power configuration to maximize performance and energy efficiency for the next time interval. In different embodiments, two types of prediction models, expert heuristic and machine learning, may be used. 
     Referring now to  FIG. 16 , shown is a block diagram of a power control logic in accordance with an embodiment of the present invention. As shown in  FIG. 16 , power control logic  1600 , which may be formed of combinations of hardware, software, and/or firmware, may be implemented as part of a larger power control unit of a processor such as a PCU. Such PCU in turn itself may be implemented as one or more microcontrollers or other control logic. In the embodiment shown, power control logic  1600  includes a performance characteristics buffer  1610 . As described herein, buffer  1610  may be configured to store incoming performance characteristics, e.g., obtained from performance/energy counters of the various cores and other logic of a processor and/or system having such processor. 
     In turn, the characteristics information is provided to a prediction logic  1620 . In different implementations, different types of prediction logic may be present. As described herein, such logic may include one or more models based on expert heuristics and/or machine learning. From the incoming characteristics information regarding current processor operation, prediction logic  1620  may generate a power configuration definition. Such definition may be used to define appropriate processor operation controls for a next operation interval. In an embodiment, such power configuration definition information may include a number of cores to be active in the next operation interval, corresponding threads to be scheduled to such cores, and voltage/frequency at which the selected cores are to operate. 
     As seen, this power configuration definition information is provided to a control logic  1630 , which may be configured to enforce the definition in the next operation interval. As such, control logic  1630  may be configured to provide control information to various processor entities, including clock generators such as one or more phase locked loops, one or more voltage regulators such as integrated voltage regulators or so forth. Still further, control information may be provided to the individual cores to indicate whether the given cores are to be powered on or off in the next operation interval. If a core is to be powered off, the core may take various actions, including saving its state to an appropriate storage to enable the core to enter into the requested low power state, gating one or more clock signals, and gating one or more power gates. For a core to become powered on in the next operation interval, such control may include ungating one or more clock signals, ungating one or more power gates, and restoring a state of the core from a given storage. Of course understand that in various embodiments, additional operations for such core low power state entry and exit may occur. Still further understand that in different implementations, a variety of different configurations of power control logic may be present. 
     For an expert heuristic model, experts identify the most relevant parameters of workloads and systems, create a prediction model to classify compute or memory bound workloads, and navigate toward the most energy efficient configurations for the identified workloads. For example, two intuitive heuristic models may be used. Due to design complexity, heuristics may only select a subset of many possible parameters, called hot states, that are featured from the most popular configurations in the design space exploration. 
     For a simple classification heuristic model (H 1 ), two parameters may be used to make decisions, e.g., instruction per second (IPS) and memory bandwidth (memBW). IPS is an indicator of core utilization while memBW directly shows memory occupancy. Workloads with low IPS and high memBW are classified as memory-bound, while high IPS and low memBW workloads are classified as compute-bound. The thresholds of high and low are adjustable, e.g., by a user in some embodiments. The decision strategy may be as follows: enable a weak power configuration (fewer cores/threads and lower voltage/frequency) for memory-bound workloads and enable a strong power configuration (which may be a baseline configuration) for compute-bound workloads. 
     A feedback classification heuristic model (H 2 ) first classifies workloads similar to H 1 . And, each classification has a preferred action; for example, memory-bound workloads will cause a weaker configuration to be enabled (first fewer cores/threads, then lower voltage/frequency), and compute-bound applications will cause a stronger configuration to be enabled. Mixed workloads have certain probabilities to go weaker or stronger. Then, an energy efficiency metric (EE) is calculated as IPS*IPS/PCL to estimate the current energy efficiency, where PCL is an estimated power consumption level derived from dominant power components such as leakage. In an embodiment, the metric may be determined by multiplying a constant (based on amount of instructions in the workload) by a reciprocal of an energy-delay product. Based on the positive or negative EE feedback from the last action, a new decision is made either to take the preferred action, to take same action as the last action, or to do nothing. 
     A comprehensive set of runtime workloads and system statistics can be as large as hundreds or thousands of features, such as the occupancy of many queue structures, the utilization of each functional unit, and so forth. To take all these combinations into account, the design space grows explosively. Therefore, embodiments may use machine learning techniques for data processing and decision making. 
     In a machine learning model, runtime statistics may be included as attributes. A multi-dimensional record is a collection of average statistical values for all attributes during a sampling time period. The most energy efficient configuration for each time interval is assigned a label with the information of cores, threads, voltage, and frequency. The model predicts the next optimal power configuration. 
     During the machine learning training process, certain performance/energy characteristics may be identified from a large amount of data and used to make intelligent automatic decisions. The offline training process takes large dimension workloads/system statistics at a given time as inputs to predict the best power configuration. The offline training process may generate a set of coefficients (or weights) that can be programmed into the power controller (e.g., by storage in a non-volatile memory) for use in real time. 
     Thus during a design or configuration process, an offline data collection occurs. This offline data collection process may be performed, e.g., by a processor designer, during the design phase and/or after manufacture. In the process, a variety of different workloads may be executed (and/or simulated) such as representative benchmark workloads to enable characterization of the workload on the processor (as determined by performance and energy parameter information). In some cases, a large number of benchmark workloads may be used to appropriately train a machine learning classifier. 
     In an example, during an offline data collection of a representative workload, multiple workload phases are identified, and during each workload phase, a data point may be generated for a particular power configuration. Then an exhaustive search for all possible configurations is performed to collect a set of representative workload data. The calculated performance and energy are used to preprocess the best energy efficient configurations, while a performance drop constraint may be enforced to filter out too much performance sacrifice. Then, each data point is labeled with its best configuration name for a later supervised learning process. 
     In different embodiments, a given set of relevant attributes may be considered. In one embodiment, these attributes include IPS, memBW, average roundtrip memory latency (memLat), memory instruction percentage (memInst), floating point instruction percentage (FPinst), ALU instruction percentage (ALUinst), pending outgoing memory requests queue occupancy (memQ), and last level cache miss rate (LLCMiss). Such attributes may best represent the workload behaviors and effectively help reduce the number of performance/energy counters. 
     In different embodiments, various offline supervised models may be used. In one example, a multi-class logistic regression model with a ridge estimator may be used to measure the relationship between more than two categorical dependent or independent variables, which exhibit good accuracy and simple implementation. In another example, a multilayer perceptron may be used. This model is an artificial neural network classifier that uses backpropagation, which may be suitable for abundant data with non-linear behaviors. The nodes are all sigmoid (logistic functions) and have at least three layers. The input layer takes all the selected attributes, and the output layer produces the optimal power configurations. As another example, a decision tree model may be used, which maintains a flowchart-like tree structure in which leaves represent labels (all possible optimal configurations), and branches are conjunctions of attributes. At each node of the tree, an attribute is selected to effectively split data points into subsets in one class and the other. 
     Once the models are trained, they are implemented into a power controller for online prediction. At runtime, performance/energy counters corresponding to the selected attributes are collected and the trained machine learning model predicts the next optimal power configuration. To improve accuracy, runtime feedback mechanisms can be used and the machine learning decision to update a power configuration may be overridden to take no action. This is so, as it is possible for the machine learning model to switch back and forth between several power configurations very frequently, resulting in high switching overhead. A saturation counter for history tracking may be used to avoid such over-sensitive reaction. Also, the machine learning model may tend to choose high energy savings while sacrificing performance too much, especially for compute-bound workloads, where weaker system resources correlate to performance directly. An IPS history register per core may be used to detect a sudden performance drop due to a power configuration change. 
     The control logic is responsible for applying the optimal power control decision to the underlying system, which involves hardware controls (e.g., voltage and frequency scaling), and software controls (e.g., cores and threads mapping). In different embodiments, various thread mapping mechanisms may be used. 
     In one embodiment, a software layer (user applications, runtime libraries, and/or operating systems) may be modified. The prediction logic provides an interface to communicate the optimal power control decision, then software adjusts thread-to-core mapping via user-level threading (fork/join), dynamic runtime libraries such as OpenMP, Posix threads, etc., task queue scheduler, or operating system thread migration. 
     An application programming interface (API) may be provided so that user applications or runtime libraries can directly access the power controller to retrieve the optimal power configuration decision. If it is better to change the power configuration, applications or runtimes adjust thread-to-core mapping. 
     For example, if an application has a large parallel loop, a programmer or a compiler can split the loop into sections and insert power-query and thread management API calls to obtain the optimal configuration for each section and parallelize the next section accordingly. A runtime framework such as OpenMP and task queue will free the programming overhead from user applications. For example, when a user application parallelizes a loop with OpenMP, the runtime can call the power-query API to obtain the optimal configuration for the loop and manage threads and cores appropriately via a thread pinning API. A task queue library can also apply similar approaches. A task queue scheduler may be used to migrate tasks automatically based on the optimal power decision. 
     Another mechanism is to augment an operating system to provide thread management for all user applications. The operating system periodically interacts with the power controller and obtains the optimal configuration. It then schedules software threads to appropriate hardware contexts. For example, assume that a user application is running eight threads on four cores; two threads per core, but the operating system is informed that a single core is the optimal configuration. Then, the operating system assigns all eight threads only on one core even though a total of four cores are available. It migrates six threads from the other three cores to the selected one core and turns off the unoccupied three cores to save energy. 
     Embodiments may also use a transparent thread migration. In some cases, a processor may include heterogeneous cores, including compute-biased cores and memory-optimized cores. Such design is based on the observation that a single core architecture cannot optimize for compute-bounded and memory-bounded workloads simultaneously. For example, conventional multiprocessors are usually optimized for compute workloads targeting for many core counts running at high frequency. However, such multiprocessors may not be energy efficient during the phases that are mostly waiting for memory accesses. Therefore, one or more cores specialized for memory-intensive phases (a memory-biased or memory-optimized core) may be provided that run at low frequency to saturate memory resources, providing the same memory performance as many compute cores. Note that such memory-biased core may be wholly transparent, both to system software (including OS) and to a customer or purchaser of the processor. For example, a given processor may include 4 compute-biased cores and a single memory-biased core. In this example, the processor product may be marketed as a multicore processor having 4 cores (with no mention made of the memory-biased core in promotional or marketing information, such that consumers are not even aware of the additional core). As such the memory-biased core may be referred to as a shadow or helper core since is transparent (and only active for a specific phase of workload execution. 
     A thread migration mechanism may be used to switch execution between the two types of cores transparently to software, both user applications and operating systems. For example, assume that a system has one memory-optimized core and four compute-optimized cores. If each compute core is two-way SMT capable, the memory-optimized core is equipped with total eight hardware contexts. The memory-optimized core contexts are visible only to hardware and completely hidden from software. And, thread migration onto the memory-optimized core contexts is handled solely by hardware. A hardware controller clones the exact same thread context between the compute core and the memory-optimized core and then resumes the executing on the new core silently. Even the operating system cannot detect the underlying thread migration. In addition, because the memory-optimized core is just another core on the same cache coherency domain, it does not give rise to any memory consistency issue at all, though it might suffer from data migrating overhead from the context migration. Note that a memory-optimized core architecture provides new opportunities to optimize energy efficiency. Because only memory-intensive workloads are executed on it, its architecture can be specialized to the extreme to achieve order of magnitude higher efficiency than a general purpose core. In some cases, the memory-optimized core implements the same ISA as compute cores. 
     Referring now to  FIG. 17 , shown is a block diagram of a processor including a hardware power control logic in accordance with another embodiment of the present invention. As illustrated in  FIG. 17 , processor  1700  is a multicore processor, which in a particular implementation may be a SoC having a variety of cores including at least some heterogeneous cores with different compute and memory capabilities. In this way, by appropriate control of active cores, a workload may be allocated amongst the cores to provide an efficient mix of power and performance. As seen, processor  1700  includes a plurality of cores  1710   0 - 1710   n . In different embodiments, these cores may be a mix of in-order and out-of-order cores, as well as compute-biased cores and one or more memory-biased cores to provide for memory bounded operation at efficient and low core power. 
     As further illustrated in  FIG. 17 , cores  1710  couple to a cache memory  1720 , which in an embodiment may be implemented as a shared cache memory such as a last level cache. Still further, processor  1700  may include an internal memory  1730 , such as may be located on a separate die of a multi-die processor package. 
     During operation, performance/energy counters included within the various cores may be configured to provide characteristic information to a power controller  1750 . In various embodiments, power controller  1750  may be implemented as a PCU that includes specialized hardware logic for performing model-based power control as described herein. 
     In the illustration of  FIG. 17 , power controller  1750  includes a characteristics buffer  1760  which may store the information incoming from the various cores. Although the scope of the present invention is not limited in this regard, such performance/energy characteristics may include instructions per cycle information, instruction mix information, load/store queue information, cache hit/miss information, memory latency information, and memory bandwidth information, among other such information. 
     As seen, buffer  1760  is coupled to a performance/energy model logic  1770 , which may, based on the incoming characteristics information, determine a performance and energy prediction. In different embodiments, performance/energy model logic  1770  may include hardware to implement a given model such as an expert heuristics-based model, a machine learning-based model and/or combinations thereof. Still with reference to  FIG. 17 , note that performance/energy logic  1770  further receives input from a configuration storage  1780 . In general, configuration storage  1780  includes information regarding possible operating characteristics, including a number of active cores (e.g., from 0 to n) and the voltage/frequency pairs for the given number of active cores. In embodiments in which performance/energy logic  1770  is a heuristic-based logic, configuration storage  1780  may further provide a heuristic storage to store one or more lookup tables having a plurality of entries each of which may be used to store workload characteristics information associated with a particular workload classification and corresponding power configuration. In embodiments in which performance/energy logic  1770  is a machine learning-based logic, configuration storage  1780  may further provide a trained model parameter storage (e.g., via a non-volatile storage) to store one or more tables having a plurality of entries each of which may be used to store trained model parameters obtained during an offline training process. 
     In some embodiments, a model for both machine learning and heuristic approaches may be implemented as an equation that includes input parameters (workload characteristics such as IPS, etc.) and a set of coefficients to provide a weight for each parameter. The equation may be used to compute a numerical value that represents an optimal configuration state for the processor for a next operation interval. This value may be used as an index to a table with different configuration parameters. In these cases, configuration storage  1780  provides a table of coefficients for each parameter. In general, the equation (or the format of the equation) is fixed. Therefore, only the coefficients may change. In the heuristic approach, the coefficients are fixed once during manufacturing. In the machine learning approach, the coefficients are obtained during offline training and programmed into the storage. When operating, the coefficients can be updated online based on machine learning. 
     Still with reference to  FIG. 17 , power controller  1750  further includes a power configuration selector  1790  which may receive a given performance energy prediction for a next operation interval and determine an appropriate next power configuration to provide operation controls to cores  1710  for the next operation interval. In the embodiment shown in  FIG. 17 , power configuration selector  1790  includes a history logic  1792 , an impact logic  1794 , and an update logic  1795 . 
     In general, history logic  1792  may be configured to analyze an incoming prediction and determine based on short-term and/or long-term history whether the prediction is appropriate and should be provided to control the cores for the next operation interval, or not. For example, a number of predictions of a particular configuration (e.g., for a reduced number of cores) may be consecutively made (e.g., 3 or more) before a configuration change to effect a reduced number of cores occurs. History logic  1792  may also be used avoid over-sensitive control of power management by reference to historical states is necessary. In one embodiment, history logic  1792  may implement a lazy switch scheme via a counter (e.g., a 2-bit saturated counter) for each possible decision. This counter is incremented when a power gating decision is made, for example. Only when the same decision is made during a predetermined number of consecutive time intervals (e.g., 3), by reference to the counter, is a power configuration update executed. In other cases, history logic  1792  may implement a history table to record prior power configuration decisions and system states. 
     Impact logic  1794  may be configured to determine an impact that predictions and configuration updates are having on the power and/or performance of the processor and to constrain or prevent predictions from being provided as a control to the cores. 
     As further shown in  FIG. 17 , power configuration selector  1790  further includes an update logic  1795 . Update logic  1795  may determine whether to enable a power configuration update based on near past decisions (e.g., with reference to entries in the history table) and far past decisions (via a long term accumulative function). Thus update logic  1795  may be configured to perform self-learning during a lifetime of processor operation (from an initial boot of the processor through multiple boot cycles (and possibly many years of operation)), by updating trained model parameters based on actual usage of the processor in the field. Understand while shown at this high level in the illustration of  FIG. 17 , many variations and alternatives are possible. 
     Referring now to  FIG. 18 , shown is a flow diagram of a method for controlling power consumption of a processor in accordance with an embodiment of the present invention. In the embodiment shown in  FIG. 18 , method  1800  may be performed by appropriate combinations of hardware, software, and/or firmware, such as a hardware power control logic as described herein, which may be implemented as part of a power controller, itself implemented as one or more microcontrollers. In one embodiment, method  1800  may be performed by a model logic that implemented a heuristic-based model. As seen, method  1800  begins by receiving workload characteristics information (block  1810 ). As described, such information may be received from performance/energy counters of various cores and other logic of a processor. In addition, configuration and power state information is also received (block  1820 ). This configuration information may correspond to a number of actively powered cores in a current operation interval and the power state thereof (e.g., a given power level at which the core is operating). In some embodiments, the power state information may further include performance state information, which may correspond to a particular voltage/frequency level at which the cores are operating. In some cases the performance state for a core may be at a guaranteed operating frequency (which is a maximum operating frequency at which a processor is guaranteed to operate), a turbo mode frequency (which is an opportunistic operating frequency higher than this guaranteed frequency), or an efficient frequency level, which is an operating frequency lower than the guaranteed frequency. 
     Still with reference to  FIG. 18 , next control passes to block  1830 , where the workload may be classified. More specifically, the workload can be classified based on some or all of the received workload characteristics information and power state information. At a high level, this workload classification may be determined to be at one of a limited number of possible levels, including a memory bounded level, a compute bounded level, or a typical operating level, which may generally correspond to a workload that is operating between a memory bounded level and a compute bounded level. Control next passes to diamond  1835  to determine whether the workload is memory bounded. Although the scope of the present invention is not limited in this regard, in an embodiment the determination of workload memory boundedness may be based on an aggregate of latency information obtained from the various cores in operation, bandwidth information associated with the memory bandwidth or so forth. 
     If it is determined that the workload is not memory bounded, control passes directly to block  1850  where current settings may be maintained. As such, in the next operation interval, the same number of cores may be powered on and these cores may continue to execute the current threads at current frequency and voltage levels. 
     Instead if it is determined that the workload is memory bounded, control passes from diamond  1835  to block  1840 , where a configuration prediction may be generated. More specifically, this configuration prediction may be for a scenario with reduced core activity, in that one or more currently active cores can be powered down and/or compute-intensive cores may be powered down in favor of one or more memory-intensive cores, to enable improved handling of the memory bound condition. Control next passes to diamond  1845  to determine whether the configuration prediction is consistent with history information. Such determination can be based on history information indicating of the appropriateness of prior predictions. If the prediction is not consistent, control passes to block  1850  where the current settings may be maintained. Note that in some cases, in addition to this history analysis a determination also may be made as to whether the predicted configuration would adversely affect performance. For example, if the configuration prediction if effected would increase a performance penalty greater than a threshold level (e.g., 5%), the new configuration may not be effected and control thus passes to block  1850 . 
     If instead it is determined that the configuration prediction is consistent with history information (and/or is not predicted to adversely affect performance by more than a threshold level), control passes to block  1860 , where threads to be executed in the next operation interval may be scheduled/rescheduled to the reduced number of cores. For example, threads currently executing on a core to be powered down may be rescheduled to cores that are to remain powered on. This is the case as in various embodiments, the cores may be multithreaded such that multiple threads can concurrently execute on a single core, e.g., via multiple logical processors, which provide appropriate hardware thread resources to enable concurrent execution. In other cases, threads may be rescheduled from certain active cores to other active cores to better accommodate and provide for efficient operation (such as moving from compute cores to memory-biased cores). Next control passes to block  1870  where the power state of the cores may be updated. That is, various control signals are sent to the cores, clock generators, voltage regulators and so forth to enable appropriate activation/deactivation of given cores. Thereafter, operation occurs in the next interval operation interval in which the threads execute on the active cores (block  1880 ). Understand while shown at this high level in the embodiment of  FIG. 18 , many variations and alternatives are possible. 
     Referring now to  FIG. 19 , shown is a flow diagram of a method for controlling power consumption of a processor in accordance with another embodiment of the present invention. As seen in  FIG. 19 , method  1900  may be performed by appropriate combinations of hardware, software, and/or firmware, such as a hardware power control logic as described herein. In one embodiment, method  1900  may be performed by a model logic that implements a machine learning-based model. Method  1900  begins by receiving workload characteristics information, e.g., from performance/energy counters within the processor (block  1910 ). In addition, configuration and power state information is also received (block  1920 ). This configuration information may correspond to a number of actively powered cores in a current operation interval and the power state thereof. 
     Next, control passes to block  1930  where trained model parameters may be obtained from a configuration storage based on the workload characteristics and power state information. More specifically, the machine learning control logic may perform a classification of the workload based on the workload characteristics information and power state information to obtain trained model parameters. These parameters may correspond to a given type of classified workload, such as compute bounded, memory bounded, typical workload or so forth. Furthermore, given the higher computing capabilities of a machine learning classifier-based logic (as compared to a heuristic-based logic), more fine-grained analysis and classification of workload level can occur. As such, in addition to compute bounded, memory bounded and typical classifications, a plurality of levels of the compute bounded classification, a plurality of levels of the memory bounded classification, in addition to a plurality of levels of a normal operation classification also can be identified and classified. 
     Still with reference to  FIG. 19 , control passes to block  1940 , where a configuration prediction can be generated from the trained model parameters. Note that in some cases, before a power configuration is updated, the machine learning logic may estimate long term and short term performance/energy impact due to previous actions taken. In an embodiment, two reward functions are implemented in the power controller for short term and long term impact evaluation. For example, if the overall reward values (a weighted combination of short term and long term rewards) indicate the model is making too aggressive predictions (and adversely affecting performance), this power configuration update does not occur. Further, as described, with regard to  FIG. 20 , self-learning may occur in which trained model parameters can be adjusted by update to the trained model parameters, e.g., to be more conservative with regard to performance impact. Thereafter, control passes to block  1950 , where threads may be scheduled (and rescheduled if needed) to the determined number of cores. In some embodiments, such thread scheduling may be performed in a hardware manner transparent to an OS or other software. In other cases, the OS itself may perform thread scheduling on the indicated number of cores. 
     Control next passes to block  1960 , where the power state of the cores may be updated. For example, various control signals are sent to the cores, clock generators, voltage regulators and so forth to enable appropriate activation/deactivation of given cores. Thereafter, operation occurs in the next interval operation interval in which the threads execute on the active cores (block  1970 ). Understand while shown at this high level in the embodiment of  FIG. 19 , many variations and alternatives are possible. 
     Understand that a machine learning logic in accordance with an embodiment of the present invention provides the ability for machine-based self-learning, such that a baseline of trained model parameters, e.g., provided upon manufacture of a processor, can be updated based on actual usage of the processor in the field, e.g., by a particular end user that operates a system including the processor with generally similar workloads during the lifetime of the processor. Furthermore, as the workload and usage of the processor varies over its lifetime, these trained model parameters can be updated based on such self-learning, to enable optimized performance and power management during processor lifetime. 
     Referring now to  FIG. 20 , shown is a flow diagram of a method for updating trained model parameters in accordance with an embodiment of the present invention. As shown in  FIG. 20 , method  2000  may be performed by appropriate combinations of hardware, software, and/or firmware, such as a hardware power control logic as described herein that implements a machine learning-based model. 
     As seen, method  2000  begins by estimating a performance/energy impact of prior configuration predictions for a workload under analysis (block  2010 ). As an example, this impact may be with regard to performance loss as a result of a reduced number of active cores (and/or reduced frequency of core operation). Next, control passes to diamond  2020  to determine whether this impact is greater than a first impact threshold. For example, in some embodiments this impact threshold may be a high impact threshold and may be set at a predetermined level, e.g., a performance impact measured in percentage of performance loss. As an example, this threshold level may be less than approximately a 10% performance loss. If it is determined that the impact is greater than the first impact threshold, control passes to block  2030  where one or more trained model parameters may be updated. More specifically, for a particular workload type under analysis, one or more trained model parameters may be updated to limit the performance impact of the power management configurations identified in the trained model parameters. As such, dynamic machine or self-learning occurs over processor lifetime, such that an appropriate balance of performance and power management can be realized. Note that in other cases, this performance/energy impact may be determined with reference to an energy-delay product, such that if reducing energy consumption causes performance to decrease (by increasing delay), e.g., by more than a threshold amount, the performance can be increased (which in turn reduces an amount of power conservation). 
     Still with reference to  FIG. 20 , if instead it is determined at block  2020  that the impact is not greater than this first impact threshold, control passes next to diamond  2040  to determine whether the impact is less than a second impact threshold. As an example, this second impact threshold may a low impact threshold and may be set a different predetermined level, e.g., less than approximately a 2-3% performance loss, in an embodiment. If it is determined that the impact is above this threshold, no update or self-learning occurs, as appropriate trained model parameters for current execution exist. Otherwise, if it is determined that the impact is less than the second impact threshold, control passes to block  2050 , where one or more trained model parameters may be updated. More specifically, for a particular workload type under analysis, one or more trained model parameters may be updated to provide for further power savings control by way of the power management configurations identified in the trained model parameters. As such, dynamic machine or self-learning occurs over processor lifetime, such that an appropriate balance of performance and power management can be realized. Understand while shown at this high level in the embodiment of  FIG. 20 , many variations and alternatives are possible. 
     Based on the particular model logic implemented (and self-learning performed during processor lifetime), many memory bound and compute bound workloads can realize optimal performance and energy efficiency with fewer active compute resources and/or lower frequencies. By identifying and selecting an optimal configuration for each particular workload, embodiments may provide energy savings of approximately 4×, while maintaining performance loss within less than approximately 5%. 
     In one embodiment a heterogeneous processor may include a plurality of compute optimized cores and one or more shadow or helper cores optimized to perform memory operations effectively. In an embodiment, the helper core may implement the same ISA as the other cores but having a simpler micro-architecture with a shallower pipeline. That is, by providing heterogeneous cores with the same ISA, a binary may be seamlessly executed on both cores. The helper core may have a shorter pipeline (e.g., 5-stages) as opposed to a larger (e.g., 20-stage) pipeline in the main core. In some instances, this heterogeneous core type may interpret complex instructions (or use microcode to execute such instructions), as performance of such instructions are not critical during memory phases of a program. In many embodiments, the helper core(s) may operate at a relatively low frequency (as compared to the primary cores) to generate sufficient memory traffic to keep the memory subsystem busy. In some embodiments, this frequency may match the frequency at which the memory system operates (e.g., at the same or substantially the same frequency at which a coupled DRAM operates). In addition, the helper core may operate at a lower voltage than compute-biased cores, such that it may operate at lower power consumption levels and more efficiently. In an embodiment, the helper core may include fewer compute resources. For example, the helper core may include only a single arithmetic logic unit (ALU), while compute-biased cores may include a plurality of ALUs (e.g., 6 or more). 
     In an embodiment, the processor may be configured to begin execution of an application on one or more compute-biased cores. In turn, the thread migration mechanism may detect program characteristics and migrate application threads to the helper core and back to the compute-biased cores without software intervention. In some cases, when performing thread switching between core types, the total thread counts remain constant, such that hardware can switch application threads dynamically from one core type to another without software intervention. In an embodiment, to simplify the software model for thread migration, the helper core may have the same number of hardware thread contexts as all compute-biased cores collectively. However, these helper core threads are only hardware visible and are not visible to software including operating system and user applications. For example, for a four compute core processor with two hardware threads in each core, the helper core may have a total of eight hardware threads. The migration of application threads to and from the helper core may be managed by hardware and is completely transparent to the running applications and operating system. 
     One example of a model that determines that a program phase is compute bound is a high instruction per cycle (IPC) value together with low memory queue occupancy. An example of a model that determines that a program phase is memory bounded is a low IPC value together with high memory queue occupancy and long average memory latency. To this end, in an embodiment a compute/memory bound metric may include determinations as to whether an instruction execution rate (e.g., IPC) exceeds a first threshold and whether a memory queue occupancy level exceeds a second threshold (in addition to other possible determinations such as average memory latency). In such embodiment as an example, a program phase may be determined to be compute bound if its IPC exceeds the first threshold and its memory queue occupancy level is less than the second threshold. Similarly, the program phase may be determined to be memory bound if its IPC is less than the first threshold and its memory queue occupancy level exceeds the second threshold. 
     A thread migration policy may determine when a thread should be migrated to and from a helper core. Since each migration involves saving and reloading the thread context, a latency overhead is incurred. Moreover, since the cores are optimized for specific execution characteristics, executing a program phase in a non-optimized core type can incur a performance penalty. 
     To enable a migration policy to have high accuracy, embodiments may use a counter-based scheme to move an application from compute bound workload region to memory bound workload region (and vice versa) with increasing certainty. In one embodiment, only when a thread has been determined to be in a particular region for a given number of consecutive periods will migration hardware cause a migration to occur. For example, in one embodiment the migration hardware may include a 2-bit counter that is updated at each analysis interval, and only when the counter is placed into a saturated state (e.g., maximum or minimum) will a migration be allowed to occur. 
     Referring now to  FIG. 21 , shown is a state diagram of a migration logic in accordance with an embodiment of the present invention. As shown in  FIG. 21 , state diagram  2100  may correspond to a logic, finite state machine or so forth configured to determine whether and when to migrate execution of threads between compute-biased cores and memory-biased cores. In the embodiment shown in  FIG. 21 , a multi-bit counter (e.g., a two bit counter)-based approach is used. During each analysis interval, a workload determination may be made as to whether the workload being executed is a memory bound workload or a compute bound workload. 
     In operation, this counter approach may begin with the assumption that a workload is compute bound and thus threads of the workload are initially scheduled to execute on the compute-biased cores. As such, the counter may initially be set to a maximum value (three in the embodiment of  FIG. 21 ). In the embodiment shown, with a saturating-type counter, execution continues on compute cores as analysis indicates that the workload type is a compute bound type. Such counter may be decremented for each determination in which a memory bound workload is determined. In the case illustrated in  FIG. 21 , three consecutive memory bound workload determinations are made to iteratively decrement the counter until it reaches a zero value and causes a thread migration to the memory-biased core(s). Once in this execution state, the workload continues to be executed on the memory-biased core until three consecutive determinations of a compute bound workload occur such that the counter value is again incremented to its maximum value of three such that a thread migration occurs to migrate the threads back to the compute-biased cores. 
     Thus as illustrated in  FIG. 21 , when the counter value is at its maximum (three), it can be ensured that a compute bound workload is executing and execution is accordingly on the compute-biased cores. Similarly, when the counter value is at its minimum (zero), it can be ensured that a memory bound workload is executing and execution is accordingly on one or more memory-biased cores. Instead when the value of the counter is decremented by one from the maximum value (to a value of two) it is likely that a compute bound workload is executing and thus execution remains on the compute-biased cores (assuming that this counter value is reached by decrementing from the maximum value). Similarly, when the value of the counter is incremented by one from the minimum value (to a value of one) it is likely that a memory bound workload is executing and thus execution remains on the memory-biased core(s) (assuming that this counter value is reached by incrementing from the minimum value). Understand while shown with this particular illustration in  FIG. 21 , the scope of the present invention is not limited in this regard and in other embodiments, additional workload classifications may be present and a migration logic may be based on other schemes. 
     Referring now to  FIG. 22 , shown is a block diagram of a memory-biased core in accordance with an embodiment of the present invention. In the embodiment shown in  FIG. 22 , core  2200  may be configured to be biased towards memory operations, such that it has relatively less compute resources and greater memory access resources. In an embodiment, while core  2200  may be of the same ISA as compute-biased cores, for execution of at least certain compute-intensive operations, microcode may be used to emulate such operations. 
     In the embodiment of  FIG. 22 , core  2200  includes a plurality of logics, functional units, storages and so forth. Understand however that the arrangement in  FIG. 22  is for a representative memory-biased core in accordance with one embodiment. Of course many other variations and alternative memory-biased cores may be present in other embodiments. 
     Furthermore, understand that a compute-biased core may generally include the same types of units and logic such as shown in  FIG. 22 . However, for a compute-biased core, different numbers of certain units may be present, and optimizations to enable improved compute capacity for a compute-biased core instead may be present. 
     As shown, core  2200  includes various units having capabilities for multiple thread resources such that the total number of hardware threads that are present within all compute-biased cores of the processor may have independent support in the memory-biased core. As such, all active threads running on all hardware threads of the compute-biased cores can instead execute on the memory-biased core concurrently. In other embodiments, multiple memory-biased cores may be provided and in such case there may be dedicated units for only a portion of the hardware threads. As shown, program counter units  2208   0 - 2208   n  is one example of a unit having multiple hardware threads (n hardware threads) (where n is the total number of hardware threads available in all of the compute-biased cores of the processor). 
     In turn, program counter unit  2208  is coupled to a fetch unit  2210  that includes a policy logic  2212 . In general, policy logic  2212  may be configured to optimally handle fetch operations based on the received program counter values from program counter unit  2208  and branch information received from a branch unit  2205 , in which various branch predictions may be performed. 
     Still with reference to  FIG. 22 , fetch unit  2210  is coupled to a cache memory  2220 , which may be a private level one instruction cache that includes an instruction translation look aside buffer (TLB)  2222 . As such, recently accessed and/or frequently accessed instructions may be stored in cache memory  2220  for more efficient access. These instructions fetched by fetch unit  2210  may be provided to a plurality of issue queues  2225   0 - 2225   n , such that each hardware thread may have a corresponding issue queue to provide instructions to a decoder unit  2230  where such incoming instructions (which in an embodiment may be in the form of macro-instructions) may be decoded and provided to a renamer/dispatcher unit  2235 . 
     As further shown in  FIG. 22 , unit  2235  in turn may be coupled to a physical register pool  2240 . Register pool  2240  includes a large number of registers, and may have sufficient storage capacity to enable the storage of active register contexts for all hardware threads. In turn, a plurality of register sets  2250   0 - 2250   n , may be provided. In an embodiment, each register set  2250  is an architectural register set for one of the n hardware threads. From renamer/dispatcher unit  2235 , the instructions and data to be used in execution of such instructions may be provided to corresponding reorder buffers (ROBs)  2250   0 - 2250   n , with a corresponding reorder buffer for each of the n hardware threads. 
     Load operations may be provided to a set of load queues  2255   0 - 2255   n , one for each of n hardware threads. Store operations may be provided to a set of store queues  2265   0 - 2265   n , one for each of n hardware threads. Note that store queues  2265  may be coupled to another cache memory  2290 , which in an embodiment may be a private level one data cache memory that further includes a data TLB  2292 . 
     Still referring to  FIG. 22 , instructions may be scheduled to a variety of different execution units via a unified scheduler  2260 . As seen, scheduler  2260  may schedule incoming instructions for execution in a single instruction multiple data (SIMD) unit  2270 , an arithmetic logic unit (ALU)  2272 , and a floating point unit (FPU)  2275 . Note that instead of providing multiple such execution resources to enable high efficiency computing operations, in the embodiment shown only a single SIMD unit, ALU and FPU are provided. It is also possible for certain high power consuming execution units such as a SIMD unit to not be present, and instead instructions for such units can be emulated in other available units. As further shown, a set of queues  2295   0 - 2295   n  (each for a corresponding hardware thread) provide an interface to a set of load store unit (LSUs)  2280   0 - 2280   n  (each for a given hardware thread), which may be used to interface with higher portions of a memory hierarchy, and provide incoming information to be used in execution of operations for storage in cache memory  2290 . 
     In addition to these physical differences between a memory-biased core and a compute-biased core, structural differences in the types of transistors and so forth that form the memory-biased and compute-biased cores may be present. For example, a memory-biased core may be formed with one or more types of transistors, while compute-biased cores may be formed of different types of transistors. In these or other cases, it is also possible for transistors of the different core types to be biased at different voltages. For example, compute-biased cores may be biased at a first bias voltage (e.g., one volt) while in turn transistors of a memory-biased core may be biased at a different, lower voltage (e.g., 0.6 V). In this way, different energy dissipation characteristics for the different types of cores may be present. Still further, a memory-biased core may have simpler (and potentially fewer) pipeline stages that operate at lower frequencies, further simplifying design for such core type. Understand while shown at this high level in the embodiment of  FIG. 22 , many variations and alternatives are possible. 
     The following examples pertain to further embodiments. 
     In one example, a processor comprises: a plurality of first cores to independently execute instructions, each of the plurality of first cores including a plurality of counters to store performance information; at least one second core to perform memory operations; and a power controller to receive performance information from at least some of the plurality of counters, determine a workload type executed on the processor based at least in part on the performance information, and based on the workload type dynamically migrate one or more threads from one or more of the plurality of first cores to the at least one second core for execution during a next operation interval. 
     In an example, the power controller is to cause the one or more of the plurality of first cores to be placed in a low power mode during the next operation interval. 
     In an example, the power controller is to dynamically migrate the one or more threads when the workload type is determined to be a memory bound workload. 
     In an example, the power controller comprises a counter, and the power controller is to update the counter in a first direction when the workload type is determined to be a first workload type and to update the counter in a second direction when the workload type is determined to be a second workload type. 
     In an example, the power controller is to dynamically migrate the one or more threads when a value of the counter at least meets a first threshold. 
     In an example, the power controller is to dynamically migrate the one or more threads from the at least one second core to the one or more of the plurality of cores when the counter value is less than or equal to a second threshold. 
     In an example, the at least one second core is heterogeneous to the plurality of first cores. 
     In an example, the at least one second core includes a first plurality of hardware thread resources, a number of the first plurality of hardware thread resources equal to a number of hardware thread resources of the plurality of first cores collectively. 
     In an example, the at least one second core comprises a single ALU and the plurality of first cores each comprises a plurality of ALUs. 
     In an example, the power controller is to cause the at least one second core to operate at a first frequency of a memory to couple to the processor and to cause the plurality of first cores to operate at a second frequency higher than the first frequency. 
     Note that the above processor can be implemented using various means. 
     In an example, the processor comprises a SoC incorporated in a user equipment touch-enabled device. 
     In another example, a system comprises a display and a memory, and includes the processor of one or more of the above examples. 
     In another example, a method comprises: determining, via a migration logic of a processor, a type of workload executing on the processor based on performance metric information received from a plurality of first cores of the processor; updating, via the migration logic, a count value in a first direction if the workload type is determined to be a first workload type and updating the count value in a second direction if the workload type is determined to be a second workload type; and migrating, via the migration logic, one or more threads from the plurality of first cores to at least one second core of the processor if the count value meets a first threshold level, and otherwise maintaining the one or more threads on the plurality of first cores. 
     In an example, the method further comprises migrating the one or more threads from the at least one second core to one or more of the plurality of first cores if the count value meets a second threshold level. 
     In an example, the plurality of first cores comprise compute-biased cores and the at least one second core comprises a memory-biased core, the first workload type comprising a memory bound workload and the second workload type comprising a compute bound workload. 
     In an example, the method further comprises controlling the at least one second core to operate at a memory matching frequency. 
     In an example, the method further comprises migrating a first plurality of threads of the workload from the plurality of first cores to the at least one second core, where the at least one second core is a single core having a first plurality of thread resources to handle the first plurality of threads. 
     In an example, the method further comprises migrating the one or more threads transparently to an operating system that executes on the processor. 
     In an example, the migration logic comprises a heuristic logic to determine the workload type further based on model information obtained from a heuristic storage of the processor. 
     In an example, the migration logic comprises a machine learning logic to determine the workload type further based on training information to be stored in a storage of the processor during manufacture of the processor. 
     In another example, a computer readable medium including instructions is to perform the method of any of the above examples. 
     In another example, a computer readable medium including data is to be used by at least one machine to fabricate at least one integrated circuit to perform the method of any one of the above examples. 
     In another example, an apparatus comprises means for performing the method of any one of the above examples. 
     In a still further example, a system comprises: a processor including: a plurality of first cores to independently execute instructions; a second core to perform memory operations; and a power controller coupled to the plurality of first cores and the second core to: receive workload characteristic information of a workload executed on a first number of active first cores in a first operation interval; classify the workload based at least in part on the workload characteristic information; and migrate one or more threads of the workload from the first number of active first cores to the second core for a next operation interval based at least in part on the workload classification of a memory bound workload, and cause one or more of the plurality of first cores to be in a low power state for the next operation interval; and a DRAM coupled to the processor. 
     In an example, the power controller is to migrate the one or more threads transparently to an operating system. 
     In an example, the power controller is to cause the second core to operate at a memory matching frequency. 
     In an example, the power controller is to generate a workload value using the workload characteristic information and a plurality of coefficients obtained from a configuration storage and classify the workload based on the workload value. 
     In an example, the plurality of first cores are to execute compute operations and the second core is to execute memory operations, the plurality of first cores collectively having a first number of hardware threads, and the second core having the first number of hardware threads, the second core including: a plurality of program counter units, each for one of the hardware threads of one of the first cores; a plurality of reorder buffers, each for one of the hardware threads of one of the first cores; a plurality of load queues, each for one of the hardware threads of one of the first cores; and a plurality of store queues, each for one of the hardware threads of one of the first cores. 
     Understand that various combinations of the above examples are possible. 
     Embodiments may be used in many different types of systems. For example, in one embodiment a communication device can be arranged to perform the various methods and techniques described herein. Of course, the scope of the present invention is not limited to a communication device, and instead other embodiments can be directed to other types of apparatus for processing instructions, or one or more machine readable media including instructions that in response to being executed on a computing device, cause the device to carry out one or more of the methods and techniques described herein. 
     Embodiments may be implemented in code and may be stored on a non-transitory storage medium having stored thereon instructions which can be used to program a system to perform the instructions. Embodiments also may be implemented in data and may be stored on a non-transitory storage medium, which if used by at least one machine, causes the at least one machine to fabricate at least one integrated circuit to perform one or more operations. The storage medium may include, but is not limited to, any type of disk including floppy disks, optical disks, solid state drives (SSDs), compact disk read-only memories (CD-ROMs), compact disk rewritables (CD-RWs), and magneto-optical disks, semiconductor devices such as read-only memories (ROMs), random access memories (RAMs) such as dynamic random access memories (DRAMs), static random access memories (SRAMs), erasable programmable read-only memories (EPROMs), flash memories, electrically erasable programmable read-only memories (EEPROMs), magnetic or optical cards, or any other type of media suitable for storing electronic instructions. 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.