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https://issues.apache.org/jira/browse/YARN-2009?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15516756#comment-15516756
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Sunil G commented on YARN-2009:
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Thank you very much [~eepayne] for sharing the thoughts.
bq.The purpose of this line of code is to set tq's unallocated resources. But
even if tq is below it's guarantee, the amount of resources that intra-queue
preemption should consider when balancing is not the queue's guarantee, it's
what the queue is already using. If tq is below its guarantee, inter-queue
preemption should be handling that.
I also thought about this in similar lines. But there was one point which i
thought it may make more sense if we use guaranteed. If queue is under used
than its capacity, our current calculation may consider more resource for
idealAssigned per app. This may yield a lesser value toBePreempted per app
(from lower priority apps). And it may be fine because there some more resource
which is available in queue for other high priority apps. So we may not need to
preempt immediately. Does this make sense?
bq.The use case I'm referencing regarding this code is not regarding 2
different users. It's regarding the same user submitting jobs of different
priorities. If user1 submits a low priority job that consumes the whole queue,
user1's headroom will be 0. Then, when user1 submits a second app at a higher
priority, this code will cause the second app to starve because user1 has
already used up its allocation.
I think i understood your point. Let me make necessary change.
> Priority support for preemption in ProportionalCapacityPreemptionPolicy
> -----------------------------------------------------------------------
>
> Key: YARN-2009
> URL: https://issues.apache.org/jira/browse/YARN-2009
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: capacityscheduler
> Reporter: Devaraj K
> Assignee: Sunil G
> Attachments: YARN-2009.0001.patch, YARN-2009.0002.patch
>
>
> While preempting containers based on the queue ideal assignment, we may need
> to consider preempting the low priority application containers first.
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