Abstract:
A method of prioritizing processing units in a system for task scheduling includes, for each processing unit of a plurality of processing units in the system, determining a value that represents a thermal condition of a location of the processing unit. It is determined which of the plurality of processing units is not fully loaded and is in a location with a most favorable thermal condition based on the value of the processing unit that represents thermal conditions of the location of the processing unit. A task is scheduled to the processing unit determined to be not fully loaded and in a location with a most favorable thermal condition based on the value of the processing unit that represents thermal conditions of the location of the processing unit.

Description:
RELATED APPLICATIONS 
     This application is a Continuation of and claims the priority benefit of U.S. application Ser. No. 14/168,782 filed Jan. 30, 2014, which claims priority under 35 U.S.C. §119 from Taiwan Patent Application 102103699, filed on Jan. 31, 2013, which is incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present inventive subject matter generally relates to task scheduling in a multi-processor computer system. 
     Unlike a uniprocessor computer system, a multi-processor computer system follows different rules to meet specific needs when performing task scheduling. For example, to achieve equilibrium of loads between processors, Completely Fair Scheduler is in use under Linux. For more details, read “Inside the Linux 2.6 Completely Fair Scheduler: Providing fair access to CPUs since 2.6.23.”, written by M. Tim Jones. 
     SUMMARY OF THE INVENTION 
     Embodiments of the inventive subject matter include a method of prioritizing processing units in a system for task scheduling, the method comprising, for each processing unit of a plurality of processing units in the system, determining a value that represents a thermal condition of a location of the processing unit. It is determined which of the plurality of processing units is not fully loaded and is in a location with a most favorable thermal condition based on the value of the processing unit that represents thermal conditions of the location of the processing unit. A task is scheduled to the processing unit determined to be not fully loaded and in a location with a most favorable thermal condition based on the value of the processing unit that represents thermal conditions of the location of the processing unit 
     In an aspect, the present invention provides a method of task scheduling based on thermal conditions at locations of processors. In a multi-processor computer system, thermal conditions at the locations of the processors are not necessarily identical because of system layout constraint. For example, in the multi-processor computer system, some processors are positioned proximate to a cooling fan or a heat-generating device and thus have an advantage or disadvantage over the other processors in terms of the working environment. The aforesaid issue is not addressed by the conventional task scheduling techniques put forth according to the prior art. 
     In view of this, the present invention includes considerations given to thermal conditions (also known as cooling conditions) at the locations of processors when performing task scheduling on the processors. According to some embodiments of the present invention, a task which has a scheduling-related priority is scheduled to processors because of favorable thermal conditions at the locations of the processors. Hence, a task is scheduled to processors with favorable thermal conditions at the locations thereof rather than processors with unfavorable thermal conditions at the locations thereof to thereby reduce heat accumulated in the system, enhance overall system performance, and reduce power consumption incurred in heat dissipation. 
     The concept about “thermal conditions at the locations of processors” refers to ambient conditions at the locations (such as processor slots) of the processors, for example, thermal contribution or cooling contribution of a heating source (such as another processor, memory module, or power supply) outside the processor or a cooling source (such as a fan or heat dissipation module) to the locations of the processors, or the fact that the processors are upstream or downstream from a heat-dissipating path (such as a cooling air current) in the system. 
     For an illustrative purpose, “thermal conditions at locations of processors” as disclosed in the present invention in another aspect refer to ambient conditions which are considered at a system design stage and serve as default parameters. For example, they come in the form of a lookup table accessible by an operating system, thus dispensing the need to consider situations in which the processors at the locations are operating (for example, temperature and consumed power while operation is underway). 
     In another embodiment of the present invention, a task scheduling method applies to a computer system and comprises:
         prioritizing the first processor and the second processor based on thermal conditions of the first zone and the second zone, respectively; and   scheduling one of a plurality of tasks to the first processor and the second processor according to the prioritization performed in the aforesaid step.       

     Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussion of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment. 
     Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention will be readily understood, amore particular description of the invention briefly described above will be rendered by reference to embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings. 
         FIG. 1  is a schematic view of a computer system according to a specific embodiment of the present invention; 
         FIG. 2  is a schematic view of an operating system in the computer system according to a specific embodiment of the present invention; 
         FIG. 3  is a schematic view of the layout in the computer system according to a specific embodiment of the present invention; 
         FIG. 4  is a flow chart of a method according to a specific embodiment of the present invention; and 
         FIG. 5  is a flow chart of the method according to another specific embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
     As will be appreciated by one skilled in the art, the present invention may be embodied as an apparatus, a computer system, a method or a computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer-usable program code embodied in the medium. 
     Any combination of one or more computer usable or computer readable medium(s) may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-usable medium may include a propagated data signal with the computer-usable program code embodied therewith, either in baseband or as part of a carrier wave. The computer usable program code may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc. 
     Computer program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirety on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer or server may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an internet Service Provider). 
     The present invention is described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
       FIG. 1  shows the hardware framework of a computer system  100  in an embodiment. The computer system  100  comprises a power supply  102 , a central processing unit (CPU)  104 , a memory  106 , a hard disk drive  108 , a fan  110 , and an interface firmware module  112 . For information about the other fundamental framework and components of the computer system  100 , make reference to a typical personal computer or server, such as IBM&#39;s System X, Blade Center or eServer. Details not relevant to the present invention are not described herein for the sake of brevity. 
     When the computer system  100  is operating, the power supply  102  supplies DC power to the central processing unit  104 , memory  106 , hard disk drive  108 , and fan  110 . The power supply  102 , central processing unit  104 , memory  106 , and hard disk drive  108  generate high heat while operating, and are cooled down by the fan  110 . 
     The computer system  100  is a multi-processor system and has a plurality of central processing units  104 . One or more central processing units  104  execute an operating system OS (such as Linux). Referring to  FIG. 2 , the operating system OS comprises a prioritizing unit PR and a scheduling unit TS. More related details are described later. 
     Although  FIG. 1  depicts two central processing units  104 , the present invention is not limited thereto. For details of the computer system  100 , make reference to IBM System x3755 M3 equipped with four AMD Opteron 6200 series processors each having 16 cores (maximum 2.5 GHz), 12 cores (maximum 2.6 GHz), or 8 cores (maximum 3.0 GHz). For more information about IBM System x3755 M3, read IBM System x 3755 M3:IBM Redbooks Product Guide, which is incorporated herein by reference. 
     The interface firmware module  112  may be for example, but not limited to, a read only memory (ROM) with Extensible Firmware Interface (EFI), Universal Extensible Firmware interface (UEFI), Basic Input/Output System (BIOS) or other interface. However, the present invention is not limited hereto. 
     In this embodiment, interface firmware module  112  maintains hardware data, such as ACPI table, in the computer system  100 , such that the hardware data are accessible by the operating system OS (shown in  FIG. 2 ) of the computer system  100 . Details of ACPI table are described in ACPI Table Storage Specification (v091) published by Intel and are not reiterated herein for the sake of brevity. 
       FIG. 3  further shows system layout in the computer system  100 . For an illustrative purpose,  FIG. 3  is simplified in showing the power supply  102 , two central processing units (CPU)  104   a ,  104   b , and the fan  110 . Referring to  FIG. 3 , the two central processing units  104   a ,  104   b  are mounted on processor slots  105   a ,  105   b , respectively. The actual details of the system layout are described in the aforesaid technical document, that is, IBM System x 3755 M3:IBM Redbooks Product Guide. The operating system of the computer system  100  is executed either by the central processing unit  104   a  and/or central processing unit  104   b , or by any central processing unit (not shown in  FIG. 3 ) other than the central processing units  104   a ,  104   b.    
     In the embodiment illustrated with  FIG. 3 , thermal conditions of the processor slot  105   a  are more favorable than that of the processor slot  105   b  for reasons as follows: the processor slot  105   a  is positioned proximate to the cooling fan  110  and thus receives the cooling air current to a great extent; and, with the power supply  102  generating high heat, the processor slot  105   b  positioned proximate to the power supply  102  is subjected to relatively great thermal effect from the power supply  102 . At the system design stage, a system designer uses the distance to the cooling/heating sources or sophisticated heat flow simulation in analyzing the thermal conditions of processor slots  105   a ,  105   b , assigning different effective values to different factors in thermal conditions, as shown in Table 1 below, and pre-storing the assigned effective values in interface firmware module  112  (such as ACPI DSTD table), such that the stored effective values can be accessed by the operating system OS (see  FIG. 2 ). 
     
       
         
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 factor in thermal conditions 
                 slot 105a 
                 slot 105b 
               
               
                   
                   
               
             
             
               
                   
                 power supply 102 
                 1 
                 2 
               
               
                   
                 fan 110 
                 2 
                 3 
               
               
                   
                 total 
                 3 
                 5 
               
               
                   
                   
               
             
          
         
       
     
     Effective values arising from a single factor (such as power supply) in thermal conditions mainly reflect the relative difference in the effects on thermal conditions of processor slot  105   a  and processor slot  105   b . Hence, when considering the difference in the overall thermal conditions between processor slot  105   a  and processor slot  105   b , it is feasible to add together the effective values of different factors in thermal conditions. However, a system designer can assign different weights to different factors in thermal conditions, though the present invention is not limited thereto. 
     In another embodiment, processor slots  105   a ,  105   b  are usually adjacent to each other, and processors  104   a ,  104   b  mounted thereon generate plenty of heat while operating and thus affect each other. As a result, if specific data (such as nominal consumed power) pertaining to processors  104   a ,  104   b  are known during the system design state, it will be feasible to give considerations to the effect of operation of processors fixed to adjacent slots on the slot thermal conditions as illustrated with Table 2 below. For example, it is feasible to consider the effect on slot  105   a  of operation of central processing unit  104   b  fixed to slot  105   b . Processors  104   a ,  104   b  are not necessarily identical, and thus processors  104   a ,  104   b  are likely to have different effects on slot thermal conditions, as illustrated with Table 2 below. 
     
       
         
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 factor in thermal condition 
                 slot 105a 
                 slot 105b 
               
               
                   
                   
               
             
             
               
                   
                 power supply 102 
                 1 
                 2 
               
               
                   
                 fan 110 
                 2 
                 3 
               
               
                   
                 central processing unit 104a 
                 0 
                 2 
               
               
                   
                 central processing unit 104b 
                 5 
                 0 
               
               
                   
                 total 
                 8 
                 7 
               
               
                   
                   
               
             
          
         
       
     
     Hence, all the thermal conditions of slot  105   a  and slot  105   b  can be quantized and thereby be subjected to subsequent automated judgment or applied to data processing. Not only is it feasible, as described before, to simulate and specify all the thermal conditions of slot  105   a  and slot  105   b  during the system design stage, but factors in thermal conditions can also be measured and identified while the system is operating. 
     The task scheduling method in an embodiment of the present invention is illustrated with the flow chart shown in  FIG. 4  and comprises the steps as follows:
         Step  400 : a system designer determines respective thermal conditions of processor slots  105   a ,  105   b  and specifies corresponding values to be written to or updated in the interface firmware module  112 . Alternatively, the system designer specifies corresponding values for the respective thermal conditions of slots  105   a ,  105   b  according to the model numbers of various hardware components (such as fans of different powers), such that the operating system OS selects one of the values as needed. Preferably, interface firmware module  112  has ACPI DSTD table for storing thermal condition values of slots  105   a ,  105   b , and the stored thermal condition values are accessible by the operating system OS through UEFI.   Step  402 : computer system  100  boots, wherein operating system OS undergoes initialization, accesses interface firmware module  112  through and selects appropriate thermal condition values of processor slots  105   a ,  105   b  (see Table 1 or Table 2).   Step  404 : the prioritizing unit PR in operating system OS prioritizes processors  104   a ,  104   b  mounted on processor slots  105   a ,  105   b  according to thermal condition values attributed to processor slots  105   a ,  105   b  and obtained in step  402 . In this embodiment, the prioritizing unit PR gives priority to the processor mounted on the processor slot with favorable thermal conditions (i.e., with the least total of thermal condition values, as shown in Table 1 or Table 2). Take the thermal condition values in Table 2 as an example, the processor  104   b  mounted on processor slot  105   b  has priority over the processor  104   a  mounted on processor slot  105   a . Although  FIG. 3  shows only two processors  104   a ,  104   b  and two processor slots  105   a ,  105   b  corresponding thereto for an illustrative purpose, in an embodiment where computer system  100  has at least three processors (and corresponding processor slots), the prioritizing unit PR prioritizes all the processors according to the thermal conditions of the processor slots, respectively.   Step  406 : the scheduling unit TS in operating system OS determines whether processor  104   b  is fully loaded according to the priority provided by the prioritizing unit PR in step  404 , for example, processor  104   b  has priority over processor  104   a . If processor  104   b  is not fully loaded, the task will be scheduled to processor  104   b  (step  408 ). If processor  104   b  is fully loaded, the task will be scheduled to the processor with the second priority (i.e., processor  104   a ) in the prioritization performed by the prioritizing unit PR (step  410 ).       

     The implementation of the task scheduling method performed with the scheduling unit TS in operating system OS, illustrated with the flow chart shown in  FIG. 5 , and disclosed in another embodiment of the present invention, can continue from step  404  of  FIG. 4 , when compared with step  406 .
         Step  506 : the scheduling unit TS in operating system OS schedules a task to processor  104   a  according to a predetermined rule (such as round-robin algorithm). In this step, it is feasible for the scheduling unit TS to first ignore the prioritization performed by the prioritizing unit PR.   Step  508 : in an embodiment, the scheduling unit TS determines whether processor  104   a  has first priority in the prioritization performed by the prioritizing unit PR in step  404 . In another embodiment, the scheduling unit TS determines whether processor  104   a  has not yet been fully loaded and whether processor  104   a  has first priority in the prioritization performed by the prioritizing unit PR in step  404 . In the two aforesaid embodiments, keep the task schedule of step  506  (step  510 ) if the determination is affirmative, and a negative determination indicates either that processor  104   a  has been fully loaded or that processor  104   a  has not yet been fully loaded but does not have first priority, thereby returning the task to the scheduling unit TS (step  512 ) and going back to step  506  for rescheduling the task to another processor until the process flow of the method goes to step  510 .       

     In the aforesaid embodiments, task scheduling is based on the thermal conditions (or ambient conditions) of the slots. According to the present invention, no consideration is given to the heat generated from processors mounted on the slots, as far as the thermal conditions of the slots are concerned. In Table 2, considerations are given to the processors mounted on adjacent slots. For example, for the thermal condition of the slot  105 A, no consideration is given to the heat generated from the processor  104 A but to the processor  104 B which is mounted on the adjacent slot  105   b . However, the teaching (i.e., the thermal conditions of the slots) of the present invention can also be integrated into the prior art in terms of task scheduling based on the temperature (i.e., the present thermal conditions) of the processors mounted on the slots, and the present invention is not limited thereto. 
     The foregoing preferred embodiments are provided to illustrate and disclose the technical features of the present invention, and are not intended to be restrictive of the scope of the present invention. Hence, all equivalent variations or modifications made to the foregoing embodiments without departing from the spirit embodied in the disclosure of the present invention should fall within the scope of the present invention as set forth in the appended claims.