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https://issues.apache.org/jira/browse/HDFS-7325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14198776#comment-14198776
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Colin Patrick McCabe commented on HDFS-7325:
--------------------------------------------

bq. The < above should be <=. 

One tricky thing here is that the patch moves this block after the 
{{numAllocated--}}.  So I believe this should be correct... 

bq. How about simply including the change in HDFS-7358 and resolving this?

OK.

> 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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