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https://issues.apache.org/jira/browse/YARN-8020?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wangda Tan updated YARN-8020:
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Issue Type: Sub-task (was: Bug)
Parent: YARN-8159
> when DRF is used, preemption does not trigger due to incorrect idealAssigned
> ----------------------------------------------------------------------------
>
> Key: YARN-8020
> URL: https://issues.apache.org/jira/browse/YARN-8020
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: kyungwan nam
> Priority: Major
>
> I’ve met that Inter Queue Preemption does not work.
> It happens when DRF is used and submitting application with a large number of
> vcores.
> IMHO, idealAssigned can be set incorrectly by following code.
> {code}
> // This function "accepts" all the resources it can (pending) and return
> // the unused ones
> Resource offer(Resource avail, ResourceCalculator rc,
> Resource clusterResource, boolean considersReservedResource) {
> Resource absMaxCapIdealAssignedDelta = Resources.componentwiseMax(
> Resources.subtract(getMax(), idealAssigned),
> Resource.newInstance(0, 0));
> // accepted = min{avail,
> // max - assigned,
> // current + pending - assigned,
> // # Make sure a queue will not get more than max of its
> // # used/guaranteed, this is to make sure preemption won't
> // # happen if all active queues are beyond their guaranteed
> // # This is for leaf queue only.
> // max(guaranteed, used) - assigned}
> // remain = avail - accepted
> Resource accepted = Resources.min(rc, clusterResource,
> absMaxCapIdealAssignedDelta,
> Resources.min(rc, clusterResource, avail, Resources
> /*
> * When we're using FifoPreemptionSelector (considerReservedResource
> * = false).
> *
> * We should deduct reserved resource from pending to avoid
> excessive
> * preemption:
> *
> * For example, if an under-utilized queue has used = reserved = 20.
> * Preemption policy will try to preempt 20 containers (which is not
> * satisfied) from different hosts.
> *
> * In FifoPreemptionSelector, there's no guarantee that preempted
> * resource can be used by pending request, so policy will preempt
> * resources repeatly.
> */
> .subtract(Resources.add(getUsed(),
> (considersReservedResource ? pending : pendingDeductReserved)),
> idealAssigned)));
> {code}
> let’s say,
> * cluster resource : <Memory:200GB, VCores:20>
> * idealAssigned(assigned): <Memory:100GB, VCores:10>
> * avail: <Memory:181GB, Vcores:1>
> * current: <Memory:19GB, Vcores:19>
> * pending: <Memory:0, Vcores:0>
> current + pending - assigned: <Memory:-181GB, Vcores:9>
> min ( avail, (current + pending - assigned) ) : <Memory:-181GB, Vcores:9>
> accepted: <Memory:-181GB, Vcores:9>
> as a result, idealAssigned will be <Memory:-81GB, VCores:19>, which does not
> trigger preemption.
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