Wiki source code of Slot Multiplier for Calculating CPU Usage in Gridengine
Last modified by Admin on 2021/10/31 17:45
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| author | version | line-number | content |
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1.1 | 1 | |
| 2 | |||
| 3 | {{toc-local/}} | ||
| 4 | |||
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5.1 | 5 | {{info}} |
| 6 | Where "cpus" are mentioned, read "cores". I'll try to make this clearer at some point. | ||
| 7 | {{/info}} | ||
| 8 | |||
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1.1 | 9 | = Introduction = |
| 10 | |||
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4.1 | 11 | When Gridengine (e.g., 8.1.9) calculates cpu usage information, it is done based on slots used and either cpu time or wallclock time. This works if each slot corresponds to a single cpu. But, if more than one cpu is allocated to a slot, this calculation does not give the desired usage information. |
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1.1 | 12 | |
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4.1 | 13 | For the purposes of this article: |
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1.1 | 14 | |
| 15 | * ((( | ||
| 16 | execd_params is configured with ACCT_RESERVED_USAGE=true and SHARETREE_RESERVED_USAGE=true so that wallclock time rather than cpu time is used | ||
| 17 | ))) | ||
| 18 | * ((( | ||
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4.1 | 19 | cpus are a dedicated resource managed by a consumable |
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1.1 | 20 | ))) |
| 21 | * ((( | ||
| 22 | jobs request the number of cpus for each slot | ||
| 23 | ))) | ||
| 24 | |||
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4.1 | 25 | with the goal of calculating cpu usage as: |
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1.1 | 26 | |
| 27 | {{noformat}} | ||
| 28 | cpu = wallclock * nslots * ncpus_per_slot | ||
| 29 | {{/noformat}} | ||
| 30 | |||
| 31 | = Usage = | ||
| 32 | |||
| 33 | The complex used to track the number of cpus used per slot is specified in the execd_params with SLOT_MULTIPLIER_NAME. E.g. | ||
| 34 | |||
| 35 | {{noformat}} | ||
| 36 | execd_params SLOT_MULTIPLIER_NAME=ncpus | ||
| 37 | {{/noformat}} | ||
| 38 | |||
| 39 | The complex would be defined as: | ||
| 40 | |||
| 41 | {{noformat}} | ||
| 42 | ncpus ncpus INT <= FORCED YES 0 1000 | ||
| 43 | {{/noformat}} | ||
| 44 | |||
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4.1 | 45 | A queue would be configured with: |
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1.1 | 46 | |
| 47 | {{noformat}} | ||
| 48 | complex_values ncpus=4 | ||
| 49 | {{/noformat}} | ||
| 50 | |||
| 51 | * 4 cpus allocatable from this queue | ||
| 52 | |||
| 53 | So, a job request for 4 slots X 16 cpus would be: | ||
| 54 | |||
| 55 | {{noformat}} | ||
| 56 | #$ -pe dev 4 | ||
| 57 | #$ -l ncpus=16 | ||
| 58 | {{/noformat}} | ||
| 59 | |||
| 60 | and a run of 30s would amount to: | ||
| 61 | |||
| 62 | (% style="margin-left: 30.0px;" %) | ||
| 63 | cpu = 30 * 4 *16 = 1920 | ||
| 64 | |||
| 65 | versus what is currently returned: | ||
| 66 | |||
| 67 | (% style="margin-left: 30.0px;" %) | ||
| 68 | cpu = 30 *4 = 120 | ||
| 69 | |||
| 70 | = Implementation = | ||
| 71 | |||
| 72 | == Changes == | ||
| 73 | |||
| 74 | source/libs/sgeobj/sge_conf.h: | ||
| 75 | |||
| 76 | * add mconf_get_slot_multiplier_name() declaration | ||
| 77 | |||
| 78 | source/libs/sgeobj/sge_conf.c: | ||
| 79 | |||
| 80 | * set slot_multiplier_name static variable to hold value set in execd_params SLOT_MULTIPLIER_NAME | ||
| 81 | * implement mconf_get_slot_multiplier_name() | ||
| 82 | |||
| 83 | source/daemons/execd/load_avg.h: | ||
| 84 | |||
| 85 | * augment build_reserved_usage() declaration to accept reference to job | ||
| 86 | |||
| 87 | source/daemons/execd/load_avg.c: | ||
| 88 | |||
| 89 | * augment build_reserved_usage() to accept reference to job | ||
| 90 | * enhance build_reserved_usage() to get slot multiplier and use it when calculating cpu usage | ||
| 91 | * add get_slot_multiplier() static function get the multiplier value if defined, or 1.0 otherwise | ||
| 92 | * update calculate_reserved_usage() to get job reference and provide it when calling build_reserved_usage() | ||
| 93 | |||
| 94 | source/daemons/execd/reaper_execd.c: | ||
| 95 | |||
| 96 | * update build_derived_final_usage() to provide job reference when calling build_reserved_usage() | ||
| 97 | |||
| 98 | Patch files (based off of [[https:~~/~~/arc.liv.ac.uk/downloads/SGE/releases/8.1.9/>>url:https://arc.liv.ac.uk/downloads/SGE/releases/8.1.9/||shape="rect"]]): | ||
| 99 | |||
| 100 | * [[attach:0001-Support-for-slot-multiplier.patch]] | ||
| 101 | |||
| 102 | == Summary == | ||
| 103 | |||
| 104 | Changes to the code are minimal. The highlights are: | ||
| 105 | |||
| 106 | * change the signature of the build_reserved_usage() function to take a job reference so that the consumable information can be obtained | ||
| 107 | * update build_reserved_usage() to use the slot multiplier value | ||
| 108 | |||
| 109 | = Conclusion = | ||
| 110 | |||
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4.1 | 111 | These changes make it possible to account for the number of cpus per slot which is critical to calculating cpu usage by wallclock. |