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https://issues.apache.org/jira/browse/HDFS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13045432#comment-13045432
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Kihwal Lee commented on HDFS-941:
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> You think 16 a good number for the socket cache (doesn't seem easily
> chanageable)?
If the client's working set size of data nodes in past several seconds is
bigger, it means lower locality. If a lot of clients are doing it, each data
node is likely to see less data locality, making page cache less effective.
This can make more reads cold and the gain from caching connections will start
to diminish. Is 16 a good number? IMO, it may actually be too big for typical
use cases, but is small enough to not cause trouble.
> Datanode xceiver protocol should allow reuse of a connection
> ------------------------------------------------------------
>
> Key: HDFS-941
> URL: https://issues.apache.org/jira/browse/HDFS-941
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: data-node, hdfs client
> Affects Versions: 0.22.0
> Reporter: Todd Lipcon
> Assignee: bc Wong
> Attachments: HDFS-941-1.patch, HDFS-941-2.patch, HDFS-941-3.patch,
> HDFS-941-3.patch, HDFS-941-4.patch, HDFS-941-5.patch, HDFS-941-6.patch,
> HDFS-941-6.patch, HDFS-941-6.patch, hdfs-941.txt, hdfs-941.txt, hdfs941-1.png
>
>
> Right now each connection into the datanode xceiver only processes one
> operation.
> In the case that an operation leaves the stream in a well-defined state (eg a
> client reads to the end of a block successfully) the same connection could be
> reused for a second operation. This should improve random read performance
> significantly.
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