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https://issues.apache.org/jira/browse/HDFS-12137?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16088043#comment-16088043
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Kihwal Lee edited comment on HDFS-12137 at 7/14/17 8:56 PM:
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Thanks for the review, [~xiaochen] and the patch, Daryn.
Just committed to trunk, branch-2 and branch-2.8.
was (Author: kihwal):
Thanks for the review, [~xiaochen] and the patch, Daryn.
> DN dataset lock should be fair
> ------------------------------
>
> Key: HDFS-12137
> URL: https://issues.apache.org/jira/browse/HDFS-12137
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 2.8.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Priority: Critical
> Fix For: 2.9.0, 3.0.0-beta1, 2.8.3
>
> Attachments: HDFS-12137.branch-2.patch, HDFS-12137.trunk.patch,
> HDFS-12137.trunk.patch
>
>
> The dataset lock is very highly contended. The unfair nature can be
> especially harmful to the heartbeat handling. Under high loads, partially
> expose by HDFS-12136 introducing disk i/o within the lock, the heartbeat
> handling thread may process commands so slowly due to the contention that the
> node becomes stale or falsely declared dead. The unfair lock is not helping
> and appears to be causing frequent starvation under load.
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