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https://issues.apache.org/jira/browse/HDFS-7276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14192424#comment-14192424
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Tsz Wo Nicholas Sze commented on HDFS-7276:
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> ... The extra complexity (and poor performance during startup) needed to
> dynamically add managers doesn't seem worth it, in my opinion.... am I
> missing something?
When the array size is large and the arrays are infrequently used, we may not
want to recycle them since it wastes memory. Therefore, we have count
threshold.
> Can you explain how a deadlock would occur if this were notify rather than
> notifyAll? ...
This is a simple concurrent problem. I believe you can work out a deadlock
example. If not, please feel free to come back to me.
> Limit the number of byte arrays used by DFSOutputStream
> -------------------------------------------------------
>
> Key: HDFS-7276
> URL: https://issues.apache.org/jira/browse/HDFS-7276
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Tsz Wo Nicholas Sze
> Attachments: h7276_20141021.patch, h7276_20141022.patch,
> h7276_20141023.patch, h7276_20141024.patch, h7276_20141027.patch,
> h7276_20141027b.patch, h7276_20141028.patch, h7276_20141029.patch,
> h7276_20141029b.patch, h7276_20141030.patch, h7276_20141031.patch
>
>
> When there are a lot of DFSOutputStream's writing concurrently, the number of
> outstanding packets could be large. The byte arrays created by those packets
> could occupy a lot of memory.
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