# Patent

## Title
Method and apparatus for balancing project shares within job assignment and scheduling

## Abstract

A method includes associating each computing job with a group of a plurality of groups, and associating each group with a minimum promised utilization. Further, the method includes determining a present utilization for each group having at least one job ready for scheduling, each job being associated with at least one required resource, the present utilization for a given group comprising a total amount of a promised resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization associated with the given group. A first computing job selected for scheduling is one that is ready for scheduling and is the computing job having a highest static priority within a group having a lowest present utilization. A subset of computing nodes able to satisfy the at least one required resource associated with the first computing job is identified.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a continuation in part application of the following U.S. applications filed on May 13, 2005, and assigned to the assignee of the present application: “Method and Apparatus for Scheduling Computing Jobs in a Computing System” (U.S. patent application Ser. No. 11/128,802); “Method and Apparatus for Multidimensional Priority Determination for Job Scheduling” (U.S. patent application Ser. No. 11/128,629), now U.S. Pat. No. 7,743,378; “Method and Apparatus for Job Assignment and Scheduling Using Advance Reservation, Backfilling, and Preemption” (U.S. patent application Ser. No. 11/128,725); and “Method and Apparatus for Flexible Job Preemption” (U.S. patent application Ser. No. 11/128,655), now U.S. Pat. No. 7,752,622.


BACKGROUND
The sizes and capabilities of computing systems vary from systems that fit on a desktop and have a few microprocessors to large computing systems that fill large rooms and have specialized electrical and cooling requirements. Such large systems may have as many as 20,000 computing nodes or more, with each computing node having up to 40 or more central processing units (CPU's) cooperatively executing computing jobs. Computing nodes are computing entities with various resources that may be used to execute computing jobs.
As computing systems continue to grow in size and complexity, scheduling computing jobs within those computing systems becomes increasingly important, in order to efficiently use the available resources in the system.
Traditionally, scheduling within a computing system includes examining computing jobs in the order the jobs arrive to determine whether the proper resources are available to execute a specific computing job immediately. If sufficient resources are not available to execute the computing job immediately, the computing job is placed in a waiting queue until the required, previously unavailable resources become available. Once the required resources become available, the computing job is removed from the waiting queue and executed on a computing node having the required resources.
SUMMARY
In general, in one aspect, the invention relates to a method for scheduling computing jobs. The method includes associating each computing job in the system with a group of computing jobs of a plurality of groups of computing jobs, and associating each group of the plurality of groups with a corresponding minimum promised utilization. Further, the method includes determining a present utilization for each group of the plurality of groups having at least one job ready for scheduling, each job being associated with at least one required resource. The present utilization for a given group includes a total amount of a promised resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization associated with the given group.
In general, in one aspect, the invention relates to a computing system including multiple computing nodes for executing multiple computing jobs, and a scheduler configured to schedule the multiple computing jobs. Scheduling is accomplished within the computing system by associating each computing job in the system with a group of a plurality of groups, and associating each group of the plurality of groups with a corresponding minimum promised utilization. Further, the method includes determining a present utilization for each group of the plurality of groups having at least one job ready for scheduling, each job being associated with at least one required resource, the present utilization for a given group comprising a total amount of a promised resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization associated with the given group.
In one or more embodiments, a static priority is calculated for each computing job ready for scheduling. A first computing job selected for scheduling is one that is ready for scheduling and is the computing job having the highest static priority within a group having a lowest present utilization. A subset of computing nodes able to satisfy the at least one required resource associated with the first computing job is identified. The method includes predicting, for each of the nodes within the subset of computing nodes, an earliest predicted completion time that the first computing job can be completed, taking into account already scheduled jobs; and scheduling execution of the first computing job on the node within the subset of computing nodes having the earliest predicted completion time, wherein the execution of the first computing job is scheduled to occur during a first time period beginning at a time selected from the group consisting of a current time and a future time.
Other aspects of the invention will be apparent from the following description and the appended claims.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a block diagram of a computing system according to one or more embodiments of the invention.
FIG. 2 shows a timeline representing a portion of a schedule according to one or more embodiments of the invention.
FIG. 3 shows a flowchart of a method for scheduling computing jobs according to one or more embodiments of the invention.
FIG. 4 shows a flowchart of a method according to one or more embodiments of the invention.
FIG. 5 shows a flowchart of a method according to one or more embodiments of the invention.
FIG. 6 is a flowchart of a method according to one or more embodiments of the invention.



DETAILED DESCRIPTION
Exemplary embodiments of the invention will be described with reference to the accompanying drawings. Like items in the drawings are shown with the same reference numbers.
In one or more embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating this disclosure.
In this specification, it is intended that the term “coupled” describe devices which interact with each other, directly or indirectly. For example, first and second devices that interact with each other through a transmission line between the two devices are directly coupled. Further, first and second devices that have intermediate devices disposed between them, and interact with one another through those intermediate devices, are indirectly coupled. In both situations, the first and second devices are considered coupled.
In general, embodiments of the invention relate to a method and apparatus for scheduling computing jobs. In one or more embodiments of the invention, the method includes associating each computing job in the system with a group of a plurality of groups, and associating each group of the plurality of groups with a minimum promised utilization. Further, in one or more embodiments of the invention, the method includes determining a present utilization for each group of the plurality of groups having at least one job ready for scheduling, each job being associated with at least one required resource, the present utilization for a given group comprising a total amount of a promised resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization associated with the given group.
A static priority is calculated for each computing job ready for scheduling. A first computing job selected for scheduling is one that is ready for scheduling and is the computing job having the highest static priority within a group having a lowest present utilization. A subset of computing nodes able to satisfy the at least one required resource associated with the first computing job is identified. The method includes predicting, for each of the nodes within the subset of computing nodes, an earliest predicted completion time that the first computing job can be completed, taking into account already scheduled jobs; and scheduling execution of the first computing job on the node within the subset of computing nodes having the earliest predicted completion time, wherein the execution of the first computing job is scheduled to occur during a first time period beginning at a time selected from the group consisting of a current time and a future time.
Scheduling is best understood in the context of an exemplary system such as system 102 of FIG. 1 in which computing nodes are arranged in various configurations.
Computing system 102 includes computing nodes 104, 106, 108, 110, and 112 each coupled to computing node 114 over transmission lines 116. Computing nodes 118, 120, 122, and 124 are each coupled to computing node 104 over transmission line 126. Computing nodes 128 and 130 are each coupled to computing node 106 over respective transmission lines 132 and 134.
Throughout this document, reference may be made to parent and child nodes. Such terminology is generally applied to tree structures, and refers to a hierarchy beginning at the “top” of the tree where a topmost node is established having only nodes below it in the tree. A node in the tree which is “above” and directly connected to another node is typically referred to as a parent node, with respect to that lower node. The lower node is typically referred to as a child node with respect to the node directly connected to and above it in the tree. Correspondingly, that same node just described as a child with respect to a node above it in the tree may be referred to as a parent node with respect to nodes immediately directly connected to and below it in the tree.
In some computing systems, such as seen in grid computing, a scheduler within the system receives computing jobs for scheduling, determines an appropriate node able to handle the computing job being scheduled, and asks the appropriate node whether it agrees to execute the computing job. In other systems such as in farm computing, a master scheduler determines the appropriate node to execute a given computing job and assigns the computing job to be executed by that appropriate node. In order to scale to thousands of nodes over an even greater number of processors, regardless of which configuration is used, the process of creating a schedule must be efficient.
In one embodiment of the invention, computing nodes are computing entities with various fixed and floating resources available that may be used to execute one or more computing jobs at any given time. Throughout this document, “fixed resource” refers to resources that are only able to be used by a single node. Examples of fixed resources include central processing units (CPU's) and memory.
A floating resource is a resource that may be moved from one node to another, as needed within the system. Floating resources may be tied to a group of nodes, or may alternatively be movable within the entire computing system, depending on the system design and restrictions that are placed on the given floating resource.
As an example, assume node 116 has three CPU's available to execute computing jobs. Since a CPU cannot be dynamically moved or allocated to a different node, CPU's are considered fixed resources. However, since a given computing job to be scheduled may additionally require floating resources in order to properly execute, the availability of one or more fixed resources, such as the proper number of CPU's, is only part of the scheduling requirements for those computing jobs. The availability of floating resources also needs to be considered.
Floating resources are available to be allocated among two or more nodes within system 102. In one or more embodiments of the invention, a floating resource may be restricted to a particular set of nodes within the system 102. Other floating resources may be able to be allocated to any of the nodes within the entire computing system 102.
One example of a floating resource is a software license. In one or more embodiments of the invention, a restricted software license “A” is available for use by node 104 and any child node of node 104. Thus, software license “A” is only available for use by nodes 104, 124, 118, 120, and 122.
In a given computing system, such as computing system 102, computing nodes may be similarly configured, may be uniquely configured, or some combination of similarly configured and uniquely configured computing nodes may exist within the system. Thus, different computing nodes may have different numbers and types of CPU's available to execute computing jobs, and may have different memory types and sizes available for use, etc. Persons of ordinary skill in the art having the benefit of this disclosure will readily be aware of how to employ the invention using computing nodes which have varying characteristics.
By way of example, node 104 has four CPU's, and 200 Megabytes of memory (e.g., random access memory (RAM), etc.) available for executing computing jobs. However, node 110 is configured with ten CPU's and 2 gigabytes of available memory. Node 108, in this example, has one CPU available, and 5 gigabytes of available memory.
Floating resources may be designated as able to be allocated to any node within computing system 102, or may instead be restricted to a given set of nodes within the system, depending on the resource and any restrictions that may be imposed by the provider of that resource.
In one or more embodiments of the invention, a floating resource includes a particular software license. In one or more embodiments of the invention, a restricted software license “A” is available for use by particular computing nodes, such as computing node 104 and any child node of node 104. Thus, that restricted software license “A” is only available for use by nodes 104, 124, 118, 120, and 122. A different software license “B” may be unrestricted and therefore available for use at any node within system 102.
To effectively provide scheduling services, a master scheduler must be aware of the resources available in the system, and where those resources are allocated at any given time. In one or more embodiments of the invention, a list of resources available in the system is maintained by the master scheduler, together with information regarding where the resource is scheduled to be allocated over a period of time. In one or more embodiments of the invention, a given node maintains a list of resources scheduled to be allocated to that given node over a period of time and makes that information available to the master scheduler, as needed.
FIG. 2 is a timeline representing a portion of a schedule according to one or more embodiments of the invention. Referring to the timeline, computing node 104 is represented by the information at 202. Computing jobs 204, 206, and 208 are shown executing over time spans 210, 212, and 214 respectively.
In the previous example, node 104 was described as having four CPU's available for executing computing jobs. Continuing with that example, those four CPU's are depicted here as four rows of the timeline, with each row representing a CPU. Computing jobs 204 and 206 are each depicted as using two CPU's, and computing job 208 is shown scheduled to use all four CPU's available on computing node 104.
The horizontal axis of the FIG. 2 timeline represents time, with the current time shown at 216. Scheduling events may be triggered in many ways. In one or more embodiments of the invention, scheduling events are triggered at regular intervals. As an example, a scheduling event is scheduled to take place in the future, at 218. In one or more embodiments of the invention, a scheduling event is triggered when the scheduler is asked to schedule a particularly important computing job.
Also shown in FIG. 2 is a portion of an example schedule for single-CPU node 108. Computing jobs 220 and 222 are shown scheduled to be executed during time periods 224 and 226 respectively.
Computing job 208 is scheduled to be executed beginning at a point in time later than the scheduled completion of computing jobs 204 and 206 which precede computing job 208. A computing job may be introduced into the scheduling cycle at a first time, such as at time 216 but may not be deemed ready for execution until a later time, such as at time 228, because of one or more dependencies associated with one or more other computing jobs, etc. Thus, a computing job must be scheduled to begin execution on or after its ready time.
It is known to those skilled in the art that computing jobs have requirements which are required to be met in order to properly execute on a computing node. It is also known to those skilled in the art that computing jobs have optional criteria which, if met, may result in a reduced overall execution time for the computing job. For example, a given computing job may require at least two CPU's to execute properly, or may be able to be split into two or more pieces that may be executed in parallel.
Splitting a job into pieces that execute in parallel often results in a shorter overall execution time, but the CPU requirement would double to four CPU's.
In the timeline of FIG. 2, computing job 222 is scheduled to execute at a future time when a required resource becomes free following its use during the execution of computing job 206. The resource needed by computing job 222 is a floating resource, and is thus allowed to move between nodes.
The floating resource in this case is limited, because a computing job needing that floating resource is delayed in execution because the floating resource was not immediately available for use. If additional similar floating resources had been available in the system at an earlier time, computing job 222 might have been able to be scheduled to begin execution at the earlier time, assuming all other required resources were also available at the earlier time.
To properly schedule computing jobs to efficiently use system resources, many considerations need to be made as to the availability of resources, the present and future utilization of resources used by the project to which the computing jobs belong, the amount of resources a given project is promised, the time a computing job is ready for execution, any dependencies a given computing job has to other computing jobs being executed by the system, etc.
FIG. 3 is a flowchart of a method for scheduling computing jobs according to one or more embodiments of the invention.
At 302, a scheduling event is triggered by the system. As previously discussed, scheduling events may be triggered in many ways. In one or more embodiments of the invention, scheduling events are triggered to take place at regular intervals. In one or more embodiments of the invention, a scheduling event is triggered when an important computing job is ready to be scheduled. Such an important computing job may be designated by assigning the computing job a very high priority as compared to other computing jobs, by indicating its importance in an information field provided for that purpose, or through other means which will be known by persons of ordinary skill in the art.
A scheduling event may also be triggered by elapsed time from a previous scheduling event. By way of example, if a previous scheduling event was triggered to occur as a result of an important computing job becoming available to be scheduled, a next scheduling event may be triggered to take place following a predetermined time interval (e.g., three microseconds, two clock cycles, etc.) from that previous scheduling event.
At 304, in one or more embodiments of the invention, computing jobs that have not yet begun execution (i.e., pending jobs) and currently executing jobs within the system (i.e., active jobs) are ranked in order of priority. In a previous scheduling event, one or more computing jobs may have been previously scheduled to execute at a future time with respect to the scheduling event discussed at 302. In addition, one or more computing jobs may have arrived to be scheduled since the last scheduling event took place. Both of those sets of computing jobs are ranked in order of priority together with active jobs.
When ranking a computing job, consideration is given to initial priority, the time a computing job has been available for scheduling (including any time spent since being scheduled to execute at a future time, if appropriate), and other factors, as appropriate to the system being scheduled, such as dependence on other computing jobs, whether the first computing job is partitionable into two or more executable pieces, preemptability, restartability, and completion deadline. Weighted averages of the various degrees of importance of the various resources as applied to given jobs are computed. The results of those computations are used to rank the various computing jobs.
By way of example, in one or more embodiments of the invention, static priority is computed using the following




  
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where

    
    
        i is an index associated with a given computing job available for scheduling,
        U represents static urgency (discussed below),
        P represents the initial priority assigned the job. and
        α and β are weighting factors designating the importance of the associated factor.
    
    


The particular value for static urgency may depend on a number of factors, such as what originated the job, the length of time the job has been waiting for execution, etc.
Computation of urgency is based on the various levels of importance associated with the values of various optimization parameters calculated for by the various computing jobs available for scheduling. Urgency for a given job to be scheduled is a weighted average of the various degrees of importance assigned to each optimization parameter calculated for that given job as shown by the following formula.




  
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where

    
    
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        αjadj the adjusted importance of a resource j and
        f(i, j) represents a value associated with a optimization parameter j, calculated for a job i
    
    


The functions f(i, j) are optimization parameter dependant, and may be determined by systems designers as appropriate. In one embodiment of the present invention, the function representing the memory requirement for a given job is




  
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Thus, with respect to the memory requirement for a given job, f(i, j) is replaced by the average memory required to properly execute the given job.
Other function values include the average number of CPU's used for a given job, the amount of time a job has been waiting for execution, the average execute time expected for this job over differently configured nodes, etc.
αjadj represents an adjusted value of an initially specified αj·αjadj is computed using




  
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At 306, all active jobs are placed on the schedule in their current positions, including the node where those active jobs are currently executing and within the time periods those active jobs are expected to occupy during execution.
At 308, a computing job which is not presently scheduled is selected for scheduling. In one or more embodiments of the invention, each computing job in the system is associated with a group. Characteristics that assign computing jobs to particular groups may vary widely. For example, jobs may be grouped according to the originator of the job, such as by business entity, department within a company, etc. In one or more embodiments of the invention, jobs are grouped by service level. In this example, business entities pay for a minimum service guarantee, wherein certain minimum resource levels are guaranteed to be provided, with additional resources being provided if available.
In one or more embodiments of the invention, the computing job selected for scheduling is the highest priority unscheduled computing job of the group of computing jobs having the lowest present utilization ratio of a promised resource.
A utilization ratio for a given resource is determined by dividing the actual amount of the promised resource presently allocated to the particular group for presently executing jobs, and dividing the actual quantity by the amount promised. By way of example, if a first group is promised ten percent of the total number of CPU's available, and the number of CPU's in the system is eighty, the number of promised CPU's is ten percent of eighty, or eight CPU's. If that first group is presently allocated ten CPU's, the utilization ratio (e.g. the actual quantity divided by the amount promised) is ten divided by eight, or 1.25. In this first example, the group is using more than its promised minimum amount of the promised resource.
Continuing on with the example, if a second group is promised thirty percent of the total number of CPU's available, and the number of CPU's in the system is 80, the number of promised CPU's is thirty percent of eighty, or twenty four CPU's. If that group is presently allocated sixteen CPU's, the utilization ratio (e.g. the actual quantity divided by the amount promised) is sixteen divided by twenty four, or 0.75. In this second example, the group is using less than its promised minimum amount of the promised resource.
Since the second group has a lower utilization ratio than the first group, the computing job selected for scheduling will come from the second group, assuming there are no other groups having a lower utilization ratio and at least one job ready for scheduling.
In this example, since the job selected for scheduling is the highest priority job in the group having the lowest present utilization ratio, the actual job selected for scheduling will be the job in the second group having the highest priority.
At 310, a list of nodes is compiled of those nodes capable of providing the fixed resources required to execute the job being scheduled. Compiling the list is accomplished by comparing the fixed resources available at each node against the resource requirements for the job being scheduled.
At 312, a node not previously examined for scheduling this particular job in this particular scheduling event is chosen from the list of nodes developed at 310. At 314, the ready time for the computing job selected is determined for the node selected at 312. As previously discussed, the ready time of a computing job is when all dependencies on other computing jobs are expected to be satisfied. Thus, if the selected computing job needs results from a previously scheduled computing job in order to execute properly, then the ready time of the selected computing job is no earlier than the time those results are expected to become available.
At 316, the earliest completion time is determined for the selected job on the selected node. This earliest completion time takes into account the predicted execution time of the job, the ready time of the job, as well as the time periods within which resources needed for job execution are available. Additional details, with respect to determining an earliest completion time for given node will be presented later. The earliest completion time determined at 316 is noted for later comparison with earliest completion times associated with other nodes for the same job in order to determine which node receives this job and the time period within which this job executes on that node.
At 318, it is determined whether all nodes capable of providing the required fixed resources have been examined to determine an earliest completion time for this job on those nodes. If there are nodes capable of providing the required fixed resources which had not been examined to determine an earliest completion time for this job, then the method proceeds again at 312, where a new node is selected for examination.
If, at 318, there are no other nodes yet to be examined, the method proceeds at 320 where the node having the earliest completion time for the selected job is selected for scheduling. At this time the selected job is scheduled to be executed by the node having the earliest completion time. The time period in which the job is scheduled begins at a time preceding that earliest completion time by an amount approximately equal to the estimated execution time.
At 321, the present utilization ratios for the group having the jobs in the scheduling queue are updated to reflect the presently scheduled being put on the schedule, and to also reflect jobs that may have recently begun executing and jobs that may have recently finished executing.
At 322, it is determined whether there are other jobs to schedule during this scheduling event. If yes, the method proceeds at 308 where the next unscheduled highest priority job belonging to the group having the lowest present utilization ratio is selected for scheduling. If, at 322, there are no jobs left to schedule in this scheduling event, the method ends.
As mentioned at 316, the earliest completion time for the selected job on a particular node is determined. Persons of ordinary skill in the art having the benefit of this disclosure will readily be aware that the earliest completion time may be determined in many ways. One such way is detailed below, and introduces the concepts of job preemption, advance reservation, and backfilling.
FIG. 4 is a flowchart of a method according to one or more embodiments of the invention.
Although it is expected that the following method for determining earliest completion time may be performed in conjunction with the method previously described with respect to FIG. 3, this method for determining earliest completion time may be performed for other reasons as well. Therefore, this method is not restricted to determining earliest completion time with respect to scheduling jobs in order of priority according to present utilization ratios.
At 402, a time period is selected for consideration. In one embodiment of the invention, the time period begins on or after the time when the job being scheduled is expected to be ready for execution. The length of the time period selected for consideration should be approximately the same length as the expected execution time of the job being scheduled.
At 404, the resources needed for the selected job are reviewed to determine which of those resources is the most important as compared to all other resources needed for the selected job, and which resource has not yet been examined during this scheduling event for this job. At this time, that most important resource for the job being scheduled is selected for examination. If it is deemed beneficial to a system designer employing the present invention, the resources required to properly execute the selected computing job may optionally be ranked as to their relative importance to each other prior to 404. Resources that cost more, or which are more scarce, for example, may have higher ranking than others costing less, or being less scarce.
In one or more embodiments of the invention, a first resource is more important than a second resource if the first resource is more costly than the second resource. In one or more embodiments of the invention, a first resource is more important than a second resource if the first resource is less available than the second resource. The importance of a resource to the selected job may be provided to the scheduler in FIG. 1, or may be determined automatically, using a computation similar to that discussed earlier with respect to static priority.
At 406, it is determined whether a sufficient amount of the selected resource is uncommitted and therefore freely available within the system during the selected time period, for the node being examined. If yes, the method proceeds at 404 where the next most important resource not yet considered is selected.
If a sufficient amount of the selected resource remains uncommitted to a job and therefore freely available within the system during the selected time period, it may be possible to free enough resources by preempting lower priority jobs or by preempting one or more jobs belonging to groups utilizing more resources than their minimum promised amount on this node or another node within the system, during the relevant time period.
Preemption of one or more jobs may take place in any number of ways, depending on the jobs being considered, and the resource utilization ratios of the groups.
First, a presently scheduled job may be preempted if the preempting job (the job being scheduled) has a priority that is greater than the priority of the job being preempted by at least a threshold amount. Second, a job may be preempted if the group the job being scheduled is not fully utilizing at least a promised minimum amount of resources, and the job being considered for preemption belongs to a group that is utilizing more than its promised minimum amount of resources, in a given time period being considered. These two preemption issues will be discussed in more detail with respect to FIGS. 5 and 6.
Returning to FIG. 4, if a sufficient amount of the selected resource does not remain uncommitted and really available within the system to execute the selected job during the selected time period, the method proceeds at 408 where a determination is made whether one or more jobs may be preempted in order to satisfy resource needs for the job being scheduled during the selected time period.
When considering whether a given resource is available, resources needed for execution of any already scheduled job are considered to be committed, including those resources required to execute jobs that are already scheduled to execute on the selected node. However, although jobs on the selected node may consume resources, those jobs are considered for preemption just like other jobs being executed on other nodes during the selected time period.
Persons of ordinary skill in the art having the benefit of this disclosure will readily understand how to determine, using the rules of the system employing the invention, whether jobs may be preempted to free up enough of the required resources to satisfy the resource needs of the job being scheduled during the selected time period. Details of one such method is described below.
If, at 408, not enough resources are available to be freed up by preempting jobs during the selected time period, the method proceeds again at 402, where a new time period is selected for consideration. If however, at 408, enough resources may be freed by preempting one or more jobs according to criteria set forth within the system, the method proceeds at 410 where scheduling and resource information within the system is updated to reflect the one or more possible preemptions, resources freed by the one or more preemptions, etc.
Recall that, at 404, the highest importance resource needed for the job being examined is selected for consideration. At 408, a determination was made that one or more jobs may be preempted to satisfy that important resource need selected at 404. At this stage, we have taken notice of one or more jobs that may be preempted in order to satisfy the resource need selected at 404. If those one or more jobs are actually preempted, it is likely that the preemption frees resources other than the resource selected at 404.
At 412, a determination is made whether there are other resources yet to consider in order to satisfy the resource needs of the selected job. If yes, the method proceeds again at 404, where the next highest important resource needed for the selected job which has not yet been considered is selected for examination. If however, all of the resources needing to be considered in order to satisfy the resource needs for the selected job have been considered, the method ends.
In a scheduling scenario such as being discussed here, the ability to preempt already executing jobs and previously scheduled jobs plays a key role. As previously discussed, jobs currently executing and jobs already on the schedule in a particular time period and allocated to a particular node for execution each consume resources on those nodes during those particular time periods.
Whether a job may be preempted from its current position on the schedule depends on a number of factors. Such factors include, but are not limited to, the priority of the job being considered for preemption as compared to the job attempting to preempt, the amount of time a currently executing job being considered for preemption has been executing as compared to its expected total time of execution, whether the job being considered for preemption may be broken into several smaller jobs, whether the job attempting to preempt may be broken into several smaller jobs, the utilization ratio during the time period being considered for the group associated with the job being scheduled, etc.
FIG. 5 is a flowchart of a method according to one or more embodiments of the invention. To execute this method, it is anticipated that a system has identified a job to be scheduled together with a resource need that has not yet been satisfied for a particular time period.
At 502, the lowest priority preemptible job already scheduled in the system during the relevant time period, whether currently executing or not, and which uses the desired resource, is selected for preemption consideration.
At 504, a determination is made whether the selected job meets minimum preemptability criteria within the system. Computing jobs considered for preemption include computing jobs that are already executing as well as computing jobs that are scheduled to execute at a future time. Thus, each of the computing jobs shown in FIG. 2, such as computing jobs 204, 206, 208, 220, and 222 may be considered for preemption. Not all of those jobs will be eligible for preemption, however, for reasons that may be different for each job.
In one or more embodiments of the invention, the importance of the first job is compared with the importance of the second job to determine, at 504, whether the static priority of the second computing job is greater than that of the first computing job.
In one or more embodiments of the invention, the first computing job is not preempted by a second computing job unless the static priority of the second computing job is substantially greater than the static priority of the first computing job. A system, such as system 102 of FIG. 1, may set a priority threshold for preemptability for one or more computing nodes in the system.
By way of example, recall that the scarcity of a floating resource necessitated scheduling computing job 222 to begin execution once computing job 206 completed. When computing job 222 was scheduled using the present invention, computing job 206 was examined for preemptability. Assume that the priority of computing job 222 is ranked at 54 on a scale of 1 to 100. If the system has a simple criteria for preemptability requiring that a first job only have a greater priority in order to preempt a second job, computing job 222 preempts computing job 206 if the priority of computing job 206 is less than 54.
In a different system having a higher preemptability criteria requiring that a preempting job have a priority at least 50 percent higher than the job being preempted, computing job 222 does not preempt computing job 206 unless computing job 206 had a priority of 36 or below.
A second example of possible preemptability criteria include whether a presently executing job may be broken into several different pieces for execution. If a computing job being examined is capable of be broken into multiple pieces, it is possible that a first piece may execute to completion, with second and later pieces being scheduled to execute at a later time, on the same computing node or a different computing node.
In one or more embodiments of the invention, some computing jobs may be broken into multiple executable pieces that are executed one after another in succession. Those multiple executable pieces need not execute immediately one after another, so long as they execute in the required order. Such a required order may, for example, be dictated by data dependencies between the different executable pieces. In a job that may be broken into different pieces for execution, data dependencies may not exist between the different pieces, making it possible for multiple pieces of the same job to concurrently execute. In one or more embodiments of the invention, a determination is made whether a computing job is able to be broken into multiple, individually executed pieces, two or more of which may concurrently execute.
A third example of preemptability criteria includes a determination of whether the computing job being considered for preemption has been executing longer or shorter than respective predetermined threshold percentages of its total expected execution time. Persons of ordinary skill in the art having the benefit of this disclosure will readily recognize that it is inefficient to preempt a computing job that is already executing unless the computing job has proceeded beyond a point where the importance of the resources freed by the preemption is outweighed by the cost of the resources already expended plus the cost of the resources consumed by reexecuting the preempted computing job in its entirety.
Jobs may also be considered for forced preemption in some circumstances. Recall that each job in the system is associated with a group, and each group is associated with a minimum promised utilization. If a job being considered for preemption is associated with a group that has a scheduled resource utilization (e.g. anticipated utilization) ratio for the time period being considered that is greater than 1.0 for a promised resource, that group is scheduled to utilize more of that promised resource than was promised. In one or more embodiments of the invention, a job associated with a group having a resource utilization ratio greater than 1.0 for the promised resource may be forcibly preempted by a job that has a resource utilization ratio for the promised resource that is less than 1.0.
In one or more embodiments of the invention, regardless of the reasons jobs may be considered for preemption, a job may not be preempted more than a maximum predetermined number of preemptions, in order to avoid causing a job to be permanently forced into the scheduling queue.
If, at 504, the execution priority of the first computing job as compared to the second computing job does not meet the priority criteria, or other criteria deemed necessary for preemption are not met, the method proceeds at 506 where it is determined whether there are other jobs to consider for preemption. If other jobs exist consider for preemption, the method proceeds again at 502. If, at 506, no other jobs exist to consider for preemption, the method ends.
If, at 504, the criteria for preemption are deemed met, the method proceeds at 508 where the job is marked as a candidate for preemption by the selected job. At 510, a determination is made whether preempting the job selected at 502 satisfies the remaining resource needs of the job being scheduled. If no, the method proceeds at 506 to determine whether other jobs may be considered for preemption. If yes, the method ends.
As previously discussed, there are two different sets of criteria which may be used for preemption. The first involves the relative priorities of the case being considered for preemption as compared to the computing job being scheduled. The second involves the resource utilizations of the groups the two computing jobs are associated with. When considering which computing job to schedule, present resource utilization is used to determine the group from which the next computing job to be scheduled is chosen. However, when determining whether to preempt an already scheduled computing job, it is the anticipated resource utilization for a particular promised resource for the time period being considered that is used to determine whether the already scheduled job is preempted.
FIG. 6 is a flowchart of a method according to one or more embodiments of the invention.
Recall from the discussion of FIG. 4 that we are trying to determine at this time is whether one or more jobs are available for preemption, in order to free resources needed to execute the job presently selected for scheduling during a time period under consideration. In order to make such a determination, a decision is made as to whether one or more jobs are preemptable using relative priorities as the preemption criteria. Following that determination, if unfulfilled resource needs remain with respect to the job being scheduled, a determination is made as to whether the resources may be freed using forced preemption based on a promised resource utilization ratio.
At 602, the jobs scheduled to be executed during the time period under consideration are reviewed, and the various groups those jobs belong to are analyzed to determine which of those groups are anticipated to have the highest utilization ratio during that time period, for a promised resource. The group having the highest utilization ratio of all groups having jobs already scheduled to execute during this time period is selected for examination with respect to preemptability.
At 604, a determination is made as to whether the selected group meets the minimum criteria for preemptability based on anticipated utilization during the time period being considered. Minimum criteria for preemptability may include, but is not limited to, the selected group being scheduled to utilize more than their minimum promised amount of the promised resource.
If at 604, a determination is made that the selected group meets minimum criteria for preemptability based on anticipated utilization of the promised resource the method proceeds at 606 when a job is selected from that group to be considered for preemption. As persons of ordinary skill having the benefit of this disclosure will be readily aware, the selected job must be one that, if preempted, will free at least one required resource, during the time period being considered.
At 608, the job is marked as a candidate for preemption. At 609, the utilization ratio associated with the group having the job being preempted is updated to reflect a new anticipated utilization expected to occur following preemption of the job selected at 606.
At 610, a determination is made as to whether the preemption of the selected job will satisfy remaining resource needs for the job being scheduled. If yes, the method ends.
If, at 604, a determination is made that the selected group does not meet minimum criteria for preemptability based on anticipated utilization, the method proceeds at 612 when that selected group is marked, for this scheduling event, as unpreemptable. The method then proceeds at 614 when a determination is made whether the group just processed or any other group in the system having jobs during the relevant time period need to be considered or reconsidered.
If, at 610, a determination was made that preempting the selected job will not satisfy the remaining resource needs of the job being scheduled, the method proceeds at 614 when a determination is made whether the group just processed or any other group in the system having jobs during the relevant time period need to be considered or reconsidered. To get to this point from 610, a job was marked as a candidate for preemption at 608, with the resource utilization ratio for the group being updated thereafter, to reflect the new anticipated resource utilization ratio following the preemption. It is still possible that the same group has other jobs which may be preempted to satisfy additional resource needs of the job being scheduled. However, those other jobs will not be examined for preemption based on utilization until all other groups having higher resource utilizations than this one have been examined, and even so only if this group still has a resource utilization ratio indicating that the group is still scheduled to be using more than its minimum promised amount of a resource.
One factor that often needs to be considered when scheduling computing jobs across many computing nodes is whether a given computing node needs to be “cleaned” prior to executing particular computing jobs. Cleaning a computing node involves security related operations designed to ensure that no process remnants or data remnants are left behind after a prior job has completed execution that the owner of the prior job might consider to be sensitive. Persons of ordinary skill in the art having the benefit of this disclosure will readily be aware of cleaning operations that may be necessary in a given situation.
For example, if a computing node is scheduled to execute a first computing job “owned” by Company A, that computing node may need special operations performed on it to “clean” the computing node prior to executing a second computing job “owned” by Company B, a competitor of Company A.
In one or more embodiments of the invention, whichever entity keeps a master schedule for a node requiring cleaning prior to executing the job owned by Company B ensures that additional time is added either to the end of the Company A job or to the beginning of the Company B job, in order to be able to satisfy the cleaning requirement.
Another factor that needs to be considered when scheduling computing jobs is time that may be required in order to prepare a node for executing a given computing job. For example, if a computing job being scheduled requires a particular operating system be running on whichever node that will execute that job, time may need to be provided in order to convert the operating system to the proper operating system, if the operating system being execute at the desired node is not the operating system needed by the succeeding computing job.
The invention provides a method and apparatus for efficiently scheduling computing jobs so that the utility of system resources is maximized. By prioritizing the incoming computing jobs and then selecting for scheduling those computing jobs in order of priority, the invention ensures that computing jobs are given the most opportunities to be selected to be scheduled on the best nodes during the best time intervals according to the importance of that computing job relative to other computing jobs ready for scheduling.
By allowing a job to be scheduled in the future (i.e., a process called forward scheduling) computing nodes are at a high level of utilization. By allowing preemption to take place, important jobs are executed at a time determined according to the job priorities. Finally, by examining the various times when resources on each appropriate computing node will be available, jobs are able to be backfilled into positions in the schedule which may be prior to other more important jobs that are delayed due to the unavailability of resources.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

## Claims

1. A method for scheduling a plurality of computing jobs in a computing system comprising:
associating each of the plurality of computing jobs in the system with a group of a plurality of groups;
associating each group of the plurality of groups with a minimum promised utilization value;
determining a present utilization value for each group of the plurality of groups having at least one job ready for scheduling, the at least one job being associated with at least one required resource, the present utilization value for a given group of the plurality of groups comprising a total amount of the at least one required resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization value associated with the given group;
calculating a static priority of each of the computing jobs ready for scheduling;
selecting a first computing job of the plurality of computing jobs that is ready for scheduling, wherein the first computing job is the computing job having a highest static priority within a group of the plurality of groups having a lowest present utilization value;
identifying a subset of computing nodes able to satisfy the at least one required resource associated with the first computing job;
predicting, for each node within the subset of computing nodes, an earliest predicted completion time for the first computing job, taking into account already scheduled jobs; and
scheduling execution of the first computing job on a node within the subset of computing nodes having the earliest predicted completion time, wherein the execution of the first computing job is scheduled to occur during a first time period, wherein the first time period begins at a time selected from the group consisting of a current time and a future time.

2. The method of claim 1 wherein each group of the plurality of groups comprises at least one selected from a group consisting of a project identifier, a group identifier, a category, an originator identifier, and an owner identifier.

3. The method of claim 1 further comprising preempting execution of a second computing job associated with a second group of the plurality of groups if the present utilization value is below 1.0 and if preempting the second computing job frees the at least one required resource and if a present utilization value of the second group for the at least one required resource for the first time period exceeds a second predetermined resource allotment associated with the second group, wherein the present utilization value of the second group comprises a total amount of the at least one required resource consumed by presently executing jobs associated with the second group divided by the minimum promised utilization value associated with the second group.

4. The method of claim 3 further comprising preempting execution of the second computing job if a static priority of the first computing job is greater than a static priority of the second computing job by at least a threshold amount and if preempting the second computing job frees at least one of the at least one required resources.

5. The method of claim 1 further comprising preempting execution of a second computing job if a static priority of the first computing job is greater than a static priority of the second computing job by at least a threshold amount and if preempting the second computing job frees at least one of the at least one required resources.

6. The method of claim 1 wherein the at least one required resource comprises at least one resource selected from a group consisting of a processor type, a supporting software, and a specified memory size.

7. The method of claim 1 wherein each of the at least one required resource is characterized by at least one selected from a group consisting of a fixed resource and a floating resource.

8. The method of claim 1 wherein the first computing job is characterized by at least one selected from a group consisting of dependence on at least one other computing job of the plurality of computing jobs, whether the first computing job is partitionable, preemptability, restartability, and completion deadline.

9. The method of claim 1 wherein calculating the static priority of each computing job comprises:
selecting a job for which to compute the static priority; and
computing at least one optimization parameter involving at least one resource selected from a list consisting of an average memory required to properly execute the selected job, an average number of CPU's used for the selected job, an amount of time the selected job has been waiting for execution, and an average execution time expected for the selected job over differently configured nodes.

10. The method of claim 1 wherein calculating the static priority of each computing job comprises:
selecting a computing job for which the static priority has not yet been computed;
computing an urgency component for the selected computing job;
computing an priority component for the selected computing job; and
adding the urgency component and the priority component together, resulting in the static priority for the selected computing job.

11. A computing system comprising:
a plurality of computing nodes for executing a plurality of computing jobs; and
a scheduler configured to schedule the plurality of computing jobs by:
associating each computing job in the system with a group of a plurality of groups; associating each group of the plurality of groups with a minimum promised utilization;
determining a present utilization for each group of the plurality of groups having at least one job ready for scheduling, the at least one job being associated with at least one required resource, the present utilization for a given group of the plurality of groups comprising a total amount of the at least one required resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization associated with the given group;
calculating a static priority of each computing job ready for scheduling;
selecting a first computing job that is ready for scheduling, wherein the first computing job is the computing job having a highest static priority within a group of the plurality of groups having a lowest present utilization;
identifying a subset of computing nodes able to satisfy the at least one required resource associated with the first computing job;
predicting, for each of the nodes within the subset of computing nodes, an earliest predicted completion time that the first computing job can be completed, taking into account already scheduled jobs; and
scheduling execution of the first computing job on a node within the subset of computing nodes having the earliest predicted completion time, wherein the execution of the first computing job is scheduled to occur during a first time period beginning at a time selected from the group consisting of a current time and a future time.

12. The computing system of claim 11 wherein each group comprises at least one selected from a group consisting of a project identifier, a group identifier, a category, an originator identifier, and an owner identifier.

13. The computing system of claim 11 wherein the scheduler is further configured to preempt execution of a second computing job associated with a second group of the plurality of groups if the present utilization is below 1.0 and if preempting the second computing job frees the at least one required resource and if a present utilization of the second group for the at least one required resource for the first time period exceeds a second predetermined resource allotment associated with the second group, wherein the present utilization of the second group comprises a total amount of the at least one required resource consumed by presently executing jobs associated with the second group divided by the minimum promised utilization associated with the second group.

14. The computing system of claim 11 wherein scheduler is further configured to preempt execution of a second computing job if a static priority of the first computing job is greater than a static priority of the second computing job by at least a threshold amount and if preempting the second computing job frees at least one of the at least one required resources.

15. The computing system of claim 13 wherein scheduler is further configured to preempt execution of the second computing job if a static priority of the first computing job is greater than a static priority of the second computing job by at least a threshold amount and if preempting the second computing job frees at least one of the at least one required resources.

16. The computing system of claim 11 wherein the at least one required resource comprises at least one resource selected from a group consisting of a processor type, a supporting software, and a specified memory size.

17. The computing system of claim 11 wherein each of the at least one required resource is characterized by at least one selected from a group consisting of a fixed resource and a floating resource.

18. The computing system of claim 11 wherein the first computing job is characterized by at least one selected from a group consisting of dependence on other computing jobs, whether the first computing job is partitionable, preemptability, restartability, and completion deadline.

19. The computing system of claim 11 wherein calculating the static priority of each computing job comprises:
selecting a job for which to compute the static priority; and
computing at least one optimization parameter involving at least one resource selected from a list consisting of an average memory required to properly execute the selected job, an average number of CPU's used for the selected job, an amount of time the selected job has been waiting for execution, and an average execution time expected for the selected job over differently configured nodes.

20. The computing system of claim 11 wherein calculating the static priority of each computing job comprises:
selecting a computing job for which the static priority has not yet been computed in this scheduling event;
computing an urgency component for the selected computing job;
computing an priority component for the selected computing job; and
adding the urgency component and the priority component together, resulting in the static priority for the selected computing job.

21. A method for scheduling a plurality of computing jobs in a computing system comprising:
associating each of the plurality of computing jobs in the system with a group of a plurality of groups;
associating each group of the plurality of groups with a minimum promised utilization value;
determining a present utilization value for each group of the plurality of groups having at least one job ready for scheduling, the at least one job being associated with at least one required resource, the present utilization value for a given group of the plurality of groups comprising a total amount of the at least one required resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization value associated with the given group;
calculating a static priority of each of the computing jobs ready for scheduling;
selecting a first computing job of the plurality of computing jobs that is ready for scheduling, wherein the first computing job is the computing job having a highest static priority within a group of the plurality of groups having a lowest present utilization value; and
scheduling execution of the first computing job on a node within a subset of computing nodes having an earliest predicted completion time, wherein the execution of the first computing job is scheduled to occur during a first time period, wherein the first time period begins at a time selected from the group consisting of a current time and a future time.

22. A computer storage having stored thereon instruction to execute a method comprising:
associating each of the plurality of computing jobs in the system with a group of a plurality of groups;
associating each group of the plurality of groups with a minimum promised utilization value;
determining a present utilization value for each group of the plurality of groups having at least one job ready for scheduling, the at least one job being associated with at least one required resource, the present utilization value for a given group of the plurality of groups comprising a total amount of the at least one required resource consumed by presently executing jobs associated with the given group divided by the minimum promised utilization value associated with the given group;
calculating a static priority of each of the computing jobs ready for scheduling;
selecting a first computing job of the plurality of computing jobs that is ready for scheduling, wherein the first computing job is the computing job having a highest static priority within a group of the plurality of groups having a lowest present utilization value; and
scheduling execution of the first computing job on a node within a subset of computing nodes having an earliest predicted completion time, wherein the execution of the first computing job is scheduled to occur during a first time period, wherein the first time period begins at a time selected from the group consisting of a current time and a future time.