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Date: Thu, 22 Sep 2016 20:28:20 +0000 (UTC)
From: "Eric Payne (JIRA)" <jira@apache.org>
To: yarn-issues@hadoop.apache.org
Message-ID: <JIRA.12711498.1398875224000.642167.1474576100614@Atlassian.JIRA>
In-Reply-To: <JIRA.12711498.1398875224000@Atlassian.JIRA>
References: <JIRA.12711498.1398875224000@Atlassian.JIRA> <JIRA.12711498.1398875224477@arcas>
Subject: [jira] [Commented] (YARN-2009) Priority support for preemption in
 ProportionalCapacityPreemptionPolicy
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archived-at: Thu, 22 Sep 2016 20:28:22 -0000


    [ https://issues.apache.org/jira/browse/YARN-2009?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15514393#comment-15514393 ] 

Eric Payne commented on YARN-2009:
----------------------------------

bq. So we could take a max(guaranteed, used). Will this be fine?
I don't think so. If {{tq.getActuallyToBePreempted}} is non-zero, it represents the amount that will be preempted from what {{tq}} is currently using, not {{tq}}'s guaranteed resources. 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.

bq. app1 of user1 used entire queue. app2 of user2 asks more resource
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.

> 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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