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https://issues.apache.org/jira/browse/YUNIKORN-3352?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated YUNIKORN-3352:
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Labels: pull-request-available (was: )
> Replace the O(n) ask-priority rescan with a pending histogram
> -------------------------------------------------------------
>
> Key: YUNIKORN-3352
> URL: https://issues.apache.org/jira/browse/YUNIKORN-3352
> Project: Apache YuniKorn
> Issue Type: Sub-task
> Components: core - scheduler
> Reporter: Dale Richardson
> Assignee: Dale Richardson
> Priority: Major
> Labels: pull-request-available
>
> {{Application.updateAskMaxPriority}} iterates the whole {{sa.requests}} map
> to recompute the highest priority among asks that are not yet allocated. It
> is called from {{allocateAsk}} on every allocation whose priority is at or
> above the current maximum, and again from {{removeAsksInternal}} on ask
> removal. Each call is O(number of asks), so scheduling N asks costs O(N^2),
> and the cost grows as an application gets larger.
> It cannot stop early, because pending and allocated asks share one map — it
> has to test {{IsAllocated()}} on every entry, and that takes a read lock each
> time. In a CPU profile of master the function is {*}55% of
> {{Application.tryAllocate}}{*}, split 56% map iteration, 22%
> {{{}IsAllocated{}}}, 15% {{{}GetPriority{}}}.
> Replace it with a per-priority histogram of pending asks
> ({{{}pendingPriorities map[int32]int{}}}), maintained incrementally as asks
> enter and leave the pending set, so {{askMaxPriority}} is available in O(1).
> {{updateAskMaxPriority}} is deleted.
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