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https://issues.apache.org/jira/browse/YARN-9278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16773792#comment-16773792
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Zhaohui Xin commented on YARN-9278:
-----------------------------------
{quote}Without introduce more complexity to FS preemption, it is already very
complicated, there are some workarounds you can try: To increase FairShare
Preemption Timeout and FairShare Preemption Threshold to reduce the chance of
preemption. This is specially useful for a large cluster, since there is more
chance to get resources just by waiting.
{quote}
If our cluster has a lot of long-running jobs, the above method is not helpful.
We have used this optimization for more than a year, which improves preemption
performance effectively. BTW, we have more than 10 clusters and most of them
have about 10K nodes.
> 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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