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https://issues.apache.org/jira/browse/YARN-10821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17367227#comment-17367227
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Andras Gyori edited comment on YARN-10821 at 6/22/21, 10:58 AM:
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[~epayne] Thanks for you review, I will get back to you with a specific
scenario. I have followed your calculation and I thought the same, however, the
total resources consumed by active users were constantly low, hence the
incorrect calculation in our case. Do you think it is worth pursuing the
investigation why this resource is 0 instead?
was (Author: gandras):
[~epayne] Thanks for you review, I will get back to you with a specific
scenario. I have followed your calculation and I thought the same, however, the
total resources consumed by active users were constantly zero, hence the
incorrect calculation in our case. Do you think it is worth pursuing the
investigation why this resource is 0 instead?
> User limit is not calculated as per definition for preemption
> -------------------------------------------------------------
>
> Key: YARN-10821
> URL: https://issues.apache.org/jira/browse/YARN-10821
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacity scheduler
> Reporter: Andras Gyori
> Assignee: Andras Gyori
> Priority: Major
> Attachments: YARN-10821.001.patch
>
>
> Minimum user limit percent (MULP) is a soft limit by definition. Preemption
> uses pending resources to determine the resources needed by a queue, which is
> calculated in LeafQueue#getTotalPendingResourcesConsideringUserLimit. This
> method involves headroom calculated by UsersManager#computeUserLimit.
> However, the pending resources for preemption are limited in an unexpected
> fashion.
> * In LeafQueue#getUserAMResourceLimitPerPartition an effective userLimit is
> calculated first:
> {code:java}
> float effectiveUserLimit = Math.max(usersManager.getUserLimit() / 100.0f,
> 1.0f / Math.max(getAbstractUsersManager().getNumActiveUsers(), 1));
> {code}
> * In UsersManager#computeUserLimit the userLimit is calculated as is
> (currentCapacity * userLimit)
> {code:java}
> Resource userLimitResource = Resources.max(resourceCalculator,
> partitionResource,
> Resources.divideAndCeil(resourceCalculator, resourceUsed,
> usersSummedByWeight),
> Resources.divideAndCeil(resourceCalculator,
> Resources.multiplyAndRoundDown(currentCapacity, getUserLimit()),
> 100));
> {code}
> The fewer users occupying the queue, the more prevalent and outstanding this
> effect will be in preemption.
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