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https://issues.apache.org/jira/browse/YARN-2009?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15522161#comment-15522161
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Sunil G edited comment on YARN-2009 at 9/26/16 9:19 AM:
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Thanks [~eepayne] for the detailed explanation. 

bq.when it comes time for the intra-queue preemption policy to preempt 
resources, it seems to me that the policy won't preempt enough resources.
Yes. I was also thinking on same line. If {{tq.used}} is less than 
{{tq.guaranteed}}, then we may hit less preemption if we use  
{{tq.guaranteed}}. Since *used* is less than *guaranteed*, there are enough 
resources available for this queue. So high priority apps will automatically 
get those resources by scheduler. 
But after thinking more, there is one case. Adding to the above mentioned 
scenario ({{tq.used}} is less than {{tq.guaranteed}}), assume another queue was 
over-utilizing resource, so current queue has to wait till inter-queue 
preemption to kick in (to get *guaranteed - used*). If inter-queue preemption 
is turned off, then current queue may not get those resources immediately. In 
such cases, I think we need to use  {{tq.used}}. I would like hear thoughts on 
this point. [~eepayne] and [~leftnoteasy]. pls share your thoughts.


was (Author: sunilg):
Thanks [~eepayne] for the detailed explanation. 

bq.when it comes time for the intra-queue preemption policy to preempt 
resources, it seems to me that the policy won't preempt enough resources.
Yes. I was also thinking on same line. If {{tq.used}} is less than 
{{tq.guaranteed}}, then we may hit less preemption if we use  
{{tq.guaranteed}}. Since *used* is less that *guaranteed*, there are enough 
resources for this queue. So high priority apps will automatically gets those 
resources by scheduler. 
But after thinking more, there is one scenario. Adding to the same scenario, 
assume another queue was over-utilizing resource, so current queue has to wait 
till inter-queue preemption to kick in. (If inter-queue preemption is turned 
off, then current queue may not get those resources immediately. In such cases, 
I think we need to use  {{tq.used}}. I would like hear thoughts on this point. 
[~eepayne] and [~leftnoteasy]. pls share your thoughts.

> 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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