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https://issues.apache.org/jira/browse/MAPREDUCE-6302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14949034#comment-14949034
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Karthik Kambatla commented on MAPREDUCE-6302:
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I see your point.
I agree that it would be nice for the two configs to be consistent; -1 could
mean disable the feature for both. Unfortunately one of the configs has already
been in a release and changes to that would be backwards incompatible.
Now, I see the following alternatives for the new config
# what the latest patch does. -1 for disable, >=0 is the wait time before
preemption
# the value provided is the wait time before preemption, and any negative
values are interpreted as zero. If folks want to disable this, they will have
to pass Long.MAX_VALUE.
Personally, I find the first one simpler to use. I do see the inconsistency
between two very similar but different configs.
> Incorrect headroom can lead to a deadlock between map and reduce allocations
> -----------------------------------------------------------------------------
>
> Key: MAPREDUCE-6302
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6302
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 2.6.0
> Reporter: mai shurong
> Assignee: Karthik Kambatla
> Priority: Critical
> Attachments: AM_log_head100000.txt.gz, AM_log_tail100000.txt.gz,
> log.txt, mr-6302-1.patch, mr-6302-2.patch, mr-6302-3.patch, mr-6302-4.patch,
> mr-6302-5.patch, mr-6302-6.patch, mr-6302-prelim.patch,
> queue_with_max163cores.png, queue_with_max263cores.png,
> queue_with_max333cores.png
>
>
> I submit a big job, which has 500 maps and 350 reduce, to a
> queue(fairscheduler) with 300 max cores. When the big mapreduce job is
> running 100% maps, the 300 reduces have occupied 300 max cores in the queue.
> And then, a map fails and retry, waiting for a core, while the 300 reduces
> are waiting for failed map to finish. So a deadlock occur. As a result, the
> job is blocked, and the later job in the queue cannot run because no
> available cores in the queue.
> I think there is the similar issue for memory of a queue .
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