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https://issues.apache.org/jira/browse/HDFS-7325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14198900#comment-14198900
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Tsz Wo Nicholas Sze commented on HDFS-7325:
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> One tricky thing here is that the patch moves this block after the
> numAllocated--. ...
Ah, you are correct. We actually do not need the "if" since "numAllocated <
maxAllocated" is always true.
> Prevent thundering herd problem in ByteArrayManager by using notify not
> notifyAll
> ---------------------------------------------------------------------------------
>
> Key: HDFS-7325
> URL: https://issues.apache.org/jira/browse/HDFS-7325
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.6.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-7325.001.patch
>
>
> Currently ByteArrayManager wakes all waiting threads whenever a byte array is
> released and count == limit. However, only one thread can proceed. With a
> large number of waiters, this will cause a thundering herd problem. (See
> http://en.wikipedia.org/wiki/Thundering_herd_problem.) We should avoid this
> by only waking a single thread.
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