Ashwin Shankar created YARN-3453:
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Summary: Fair Scheduler : Parts of preemption logic uses
DefaultResourceCalculator even in DRF mode causing thrashing
Key: YARN-3453
URL: https://issues.apache.org/jira/browse/YARN-3453
Project: Hadoop YARN
Issue Type: Bug
Components: fairscheduler
Affects Versions: 2.6.0
Reporter: Ashwin Shankar
There are two places in preemption code flow where DefaultResourceCalculator is
used, even in DRF mode.
Which basically results in more resources getting preempted than needed, and
those extra preempted containers aren’t even getting to the “starved” queue
since scheduling logic is based on DRF's Calculator.
Following are the two places :
1. {code:title=FSLeafQueue.java|borderStyle=solid}
private boolean isStarved(Resource share)
{code}
A queue shouldn’t be marked as “starved” if the dominant resource usage
is >= fair/minshare.
2. {code:title=FairScheduler.java|borderStyle=solid}
protected Resource resToPreempt(FSLeafQueue sched, long curTime)
{code}
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One more thing that I believe needs to change in DRF mode is : during a
preemption round,if preempting a few containers results in satisfying needs of
a resource type, then we should exit that preemption round, since the
containers that we just preempted should bring the dominant resource usage to
min/fair share.
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