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Posted to yarn-dev@hadoop.apache.org by "kyungwan nam (JIRA)" <ji...@apache.org> on 2018/03/10 04:52:00 UTC
[jira] [Created] (YARN-8020) when DRF is used, preemption does not
trigger due to incorrect idealAssigned
kyungwan nam created YARN-8020:
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Summary: 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: Bug
Reporter: kyungwan nam
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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