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https://issues.apache.org/jira/browse/YARN-9278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16773299#comment-16773299
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Yufei Gu commented on YARN-9278:
--------------------------------
Hi [~uranus], this seems a perf issue for a busy large cluster due to the
preemption implementation, which is iteration and check.
I would suggest lower
{{yarn.scheduler.fair.preemption.cluster-utilization-threshold}} to let
preemption kick in earlier for a large cluster. The default value is 80%, which
means preemption won't kick in until 80% resources of the whole cluster have
been used. Please be aware that low utilization threshold may cause an
unnecessary container churn, so you don't want it to be too low.
> Shuffle nodes when selecting to be preempted nodes
> --------------------------------------------------
>
> Key: YARN-9278
> URL: https://issues.apache.org/jira/browse/YARN-9278
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: fairscheduler
> Reporter: Zhaohui Xin
> Assignee: Zhaohui Xin
> Priority: Major
>
> We should *shuffle* the nodes to avoid some nodes being preempted frequently.
> Also, we should *limit* the num of nodes to make preemption more efficient.
> Just like this,
> {code:java}
> // we should not iterate all nodes, that will be very slow
> long maxTryNodeNum =
> context.getPreemptionConfig().getToBePreemptedNodeMaxNumOnce();
> if (potentialNodes.size() > maxTryNodeNum){
> Collections.shuffle(potentialNodes);
> List<FSSchedulerNode> newPotentialNodes = new ArrayList<FSSchedulerNode>();
> for (int i = 0; i < maxTryNodeNum; i++){
> newPotentialNodes.add(potentialNodes.get(i));
> }
> potentialNodes = newPotentialNodes;
> {code}
>
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