[jira] [Commented] (YARN-9278) Shuffle nodes when selecting to be preempted nodes

["Zhaohui Xin (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-9278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16772638#comment-16772638 ] 

Zhaohui Xin commented on YARN-9278:
-----------------------------------

Hi, [~yufeigu]. When preemption thread satisfies a starved container with ANY as resource name, it will find a best node in all nodes of this cluster. This will be costly when this cluster has more than 10k nodes.

I think we should limit the number of nodes in such a situation. How do you think this? :D

 

> 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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