Abstract:
Power is allocated to blades based on an estimate of the actual power they are expected to use rather than their maximum-power draw-value. To protect against situations where the estimated actual-power draw-value is exceeded, a hardware comparator monitors the blade system load against a predetermined threshold value set by a management module (MM) based on user input. If this threshold value is exceeded, a throttle latch is triggered, based on a signal from a service processor monitoring the blade system load. The output of this latch directly engages throttling. The service processor also monitors the output of the latch and communicates information regarding the throttling to the MM for evaluation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the control of throttling in blade computer systems. 
     2. Background of the Related Art 
     Operating state-of-the-art blade systems presents a significant challenge due to the newer power-hungry processor options of the blades in the system. Power supplies used in blade systems are not keeping up with the power requirements of the blades. A typical blade system may have up to 14 blades sharing power from up to four power supplies. Typically, full redundancy is built in so that in a situation where all of the blades are operating at 100%, there is sufficient power among the power supplies such that if there is a power supply failure, the other power supplies can continue to supply power to the blades without curtailing their operation. In some cases, power draws may be allowed to exceed the level at which the system is fully redundant, and in some extreme cases, the power allocation may be such that there is no redundancy at all, i.e., if one of the power supplies were to fail, significant reductions in power to the blades would have to be made. 
     When determining power allocation in a prior art blade system, assumptions are made that worst-case scenarios are occurring, that is, it is assumed that each blade will be running at 100% power at all times, and then power is allocated based upon this assumption. Typically, the maximum-power draw-value is obtained from the VPD of the blade and then power allocation is set accordingly. In reality, however, it is rare when all blades are running at 100% power and, in fact, it is estimated that only one out of every 1,000 blades will require 100% power in actual operation. Thus, there is significant power available in most situations to allocate to other blades, but because the worst-case scenario is used for each blade, this “excess power” is not utilized. 
     It would be desirable to have a method, system, and computer program product that enables actual system loads to be utilized for allocation of power in blade systems. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, power is allocated to blades based on an estimate of the actual power they are expected to use rather than their maximum-power draw-value. To protect against situations where the estimated actual-power draw-value is exceeded, a hardware comparator monitors the blade system load against a predetermined threshold value set by a management module (MM) based on user input. If this threshold value is exceeded, a throttle latch is triggered, based on a signal from a service processor monitoring the blade system load. The output of this latch directly engages throttling. The service processor also monitors the output of the latch and communicates information regarding the throttling to the MM for evaluation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a system enabling the present invention; and 
         FIG. 2  is a flowchart illustrating the steps performed in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a block diagram of a system enabling the present invention. In a preferred embodiment, each blade is equipped with the system of  FIG. 1 . Referring to  FIG. 1 , a service processor  102  having an integrated A-to-D converter  104  receives, from blade current/load sensor  106 , a voltage signal  128  proportional to the total blade current being consumed by a particular blade. Signal  128  from blade current/load sensor  106  is also presented to a first input of comparator  110 . 
     Blade current/load sensor  106  senses the current draw of the blade in which it is installed (or to which it is connected) and converts the detected current draw to signal  128 , which is an analog voltage signal. Thus, the signal  128  is an analog voltage signal proportional to the current draw of the blade. A-to-D converter  104  receives this analog signal  128  and converts it to digital form for processing by the service processor  102 . As shown in  FIG. 1  and as noted above, service processor  102  can comprise a single chip microcontroller with an integrated A-to-D converter  104 ; however, it is understood that different configurations can be utilized, e.g., a multi-chip microcontroller and/or a microcontroller with a separate analog-to-digital converter. 
     A signal  130  output from service processor  102  is input to digital-to-analog converter  108 . Signal  130  represents the digital controls used by the service processor to communicate with D-to-A converter  108 . D-to-A converter  108  converts the digital output from service processor  102  into analog signal  132 , which as described below, will be compared by comparator  110  with analog signal  128 . If desired, a simple digital potentiometer could be used to perform the same function as D-to-A converter  108  in a known manner. Analog signal  132  is input to a second input of comparator  110 . Comparator  110  is a comparator circuit that compares the magnitude of two analog signals, that is, analog signal  128  coming from total blade current/load sensor  106  and analog signal  132  being output by D-to-A converter  108 . The result of this comparison is a logic 1 or a logic 0 being output as signal  134 . As an example, the system could be configured so that if signal  132  is greater than signal  128 , output  134  will be a logic 1; otherwise, the output of  134  would be a logic 0. 
     The output  134  of comparator  110  is input to latch  112 . Latch  112  captures the occurrence of the current of the blade going above the present threshold by issuing an output signal  126  (e.g., a logic 1) when the predetermined threshold, represented by signal  132 , has been exceeded. A reset output  124  from service processor  102  is input to latch  112  and allows latch  112  to be reset when service processor  102  issues a reset command. 
     The output signal  126  from latch  112  is input to a CPLD  114 , and is also input to service processor  102 . CPLD  114  is a Complex Programmable Logic Device used to produce logical functions in a known manner. In the present invention, CPLD  114  is programmed to issue a throttle command  120  to the CPU, as well as to service processor  102 , when output signal  126  from latch  112  indicates that the total blade current/load sensed by total blade current/load sensor  106  has exceeded the threshold. The throttle command  120  issued to the CPU actually engages the throttling procedure, while the same throttle command  120  input to service processor  102  informs the service processor  102  that the system is going into a throttle mode. It is beneficial for the service processor to know that a blade is throttling because the reduction in blade function may affect customer applications being run by the blade. By knowing that a blade is throttling, and that reduced function is occurring, more power might be allocated back to the blade and a different blade might be throttled to compensate. 
     The operation of the circuit of  FIG. 1  is as follows. A user identifies the estimated actual usage for a blade that is configured with the system of  FIG. 1 . Using a keyboard or other known input device, this information is input to service processor  102  in a known manner. By inputting this estimated maximum actual usage, the user sets the threshold value that will be compared with the actual usage being made by the blade during operation. The user will take into consideration the options installed in the blade, what the particular blade is being used for, etc. It is anticipated that the estimated actual usage could be incorporated into the VPD of the blade rather than being manually input; however, currently-used blades contain data in the VPD that makes the assumption that the power usage of the blade will be equal to the power consumed when every element of the blade is operational. 
     As the blade operates, its total current/load value is sensed by total blade current/load sensor  106  and the sensor outputs a voltage  128  corresponding to the current/load level. This value is input to the A-to-D converter  104  of service processor  102  which converts the signal to a digital signal for processing by service processor  102 . For example, after the detection of an overload condition, the system may need to know what the real-time actual load measurement is, as part of a recovery algorithm. Diagnostics, initialization and other recovery implementations may need this information. 
     Signal  128  is input also to comparator  110 , and is compared with signal  132 . Signal  132  is an analog representation of the threshold value  130  that has been input to the service processor  102  by the user. If the result of the comparison indicates that the threshold value  132  is being exceeded by the actual value  128 , comparator  110  outputs a logic signal to latch  112  indicating that the blade is trying to draw more power than its pre-determined estimated maximum actual usage value. This logic value is input to latch  112 . Latch  112  is utilized because the real-time current is application-dependent and could vary at millisecond speeds. Thus, signal  134  could oscillate at millisecond speeds, rendering it difficult to be used by the service processor. Thus, this signal is latched. The latched event is an indication that an overload event occurred since the last latch reset. A near real-time reading can be achieved by performing a latch reset followed by an immediate latch read. Although the latch is shown outside CPLD  114 , the latch could also be implemented within the CPLD. Latch  112  passes a logic signal to CPLD  114  that causes CPLD  114  to issue a throttle command  120 . This throttle command is directed to the CPU, which throttles the blade to keep it from exceeding the estimated maximum actual usage value. Throttle signal  120  also is input to service processor  102  to advise it of the throttling condition. At the first occurrence of this event, the system would likely reset the circuit and look for the event to repeat. After validity that the blade really needs more power, the system should take action to re-budget more power to this blade. 
       FIG. 2  is a flowchart illustrating the steps performed in accordance with the present invention. At step  202 , the estimated maximum actual usage for each blade in the blade system is identified. At step  204 , power is allocated from the power supplies in the blade system based upon the estimated maximum actual usage for the blades. At step  206 , the maximum actual usages estimated in step  202  are set as thresholds for each blade. 
     At step  208 , the actual current draw of each blade is monitored. At step  210 , a determination is made as to whether or not any of the thresholds have been exceeded. If no thresholds have been exceeded, the process proceeds back to step  208  for continued monitoring of each blade. If, however, at step  210 , it is determined that a threshold has been exceeded, this indicates that one of the blades is beginning to operate above its maximum allocated threshold level. At step  212 , the blade that is exceeding the threshold is throttled, to keep it from exceeding this maximum. At step  214 , the throttling is reported to the management module. This can be utilized by system operators to identify occurrences of attempts to exceed power levels and, if desired, increase power levels and power level thresholds for that particular blade. The management module can also be configured, if desired, to search for underutilized or unpowered blades to increase the power budget of the throttling blade. 
     At step  216 , it is determined whether or not continued monitoring of the system is desired. If it is desired to stop monitoring, the process ends. However, if it is desired to continue monitoring, the process proceeds back to step  208  to continue monitoring the blades. 
     The present invention is described herein in a hardware embodiment and this hardware embodiment is preferred for situations where fast throttling is desired. However, the above-described steps can be implemented also using standard well-known programming techniques. The novelty of the above-described embodiment lies not in the specific programming techniques but in the use of the steps described to achieve the described results. Software programming code which embodies the present invention is typically stored in permanent storage of some type, such as permanent storage of each blade. In a client/server environment, such software programming code may be stored with storage associated with a server. The software programming code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, or hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users from the memory or storage of one computer system over a network of some type to other computer systems for use by users of such other systems. The techniques and methods for embodying software program code on physical media and/or distributing software code via networks are well known and will not be further discussed herein. 
     It will be understood that each element of the illustrations, and combinations of elements in the illustrations, can be implemented by general and/or special purpose hardware-based systems that perform the specified functions or steps, or by combinations of general and/or special-purpose hardware and computer instructions. 
     These program instructions may be provided to a processor to produce a machine, such that the instructions that execute on the processor create means for implementing the functions specified in the illustrations. The computer program instructions may be executed by a processor to cause a series of operational steps to be performed by the processor to produce a computer-implemented process such that the instructions that execute on the processor provide steps for implementing the functions specified in the illustrations. Accordingly, the figures support combinations of means for performing the specified functions, combinations of steps for performing the specified functions, and program instruction means for performing the specified functions. 
     Although the present invention has been described with respect to a specific preferred embodiment thereof, various changes and modifications may be suggested to one skilled in the art and it is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.