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https://issues.apache.org/jira/browse/YARN-8149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16436295#comment-16436295
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Thomas Graves commented on YARN-8149:
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are you going to do anything with starvation then or allocation a certain %
more then what is required? I am hesitant to remove this without doing some
major testing. I haven't had a chance to look at the latest code to
investigate.
It might be more fine now that we do continue looking at other nodes after
reservation where as originally that didn't happen. Is in queue preemption on
by default?
> Revisit behavior of Re-Reservation in Capacity Scheduler
> --------------------------------------------------------
>
> Key: YARN-8149
> URL: https://issues.apache.org/jira/browse/YARN-8149
> Project: Hadoop YARN
> Issue Type: Bug
> Reporter: Wangda Tan
> Priority: Critical
>
> Frankly speaking, I'm not sure why we need the re-reservation. The formula is
> not that easy to understand:
> Inside:
> {{org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.allocator.RegularContainerAllocator#shouldAllocOrReserveNewContainer}}
> {code:java}
> starvation = re-reservation / (#reserved-container *
> (1 - min(requested-resource / max-alloc,
> max-alloc - min-alloc / max-alloc))
> should_allocate = starvation + requiredContainers - reservedContainers >
> 0{code}
> I think we should be able to remove the starvation computation, just to check
> requiredContainers > reservedContainers should be enough.
> In a large cluster, we can easily overflow re-reservation to MAX_INT, see
> YARN-7636.
>
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