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https://issues.apache.org/jira/browse/HDFS-11514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15925461#comment-15925461
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Arpit Agarwal edited comment on HDFS-11514 at 3/15/17 3:06 AM:
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The change looks good. Just one comment - the
{{synchronized(childrenStorageInfo)}} blocks are unnecessary because the caller
of add/remove must hold {{NetworkTopology#netLock}} exclusively. I missed that
earlier.
was (Author: arpitagarwal):
The change looks good. Just one comment - the
{{synchronized(childrenStorageInfo)}} blocks are unnecessary because the caller
of add/remove must hold {{NetworkTopology#netLock}}. I missed that earlier.
> ChooseRandom can potentially be optimized
> -----------------------------------------
>
> Key: HDFS-11514
> URL: https://issues.apache.org/jira/browse/HDFS-11514
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Reporter: Chen Liang
> Assignee: Chen Liang
> Attachments: HDFS-11514.001.patch, HDFS-11514.002.patch
>
>
> Based on the offline discussion, one potential improvement to the
> {{chooseRandomWithStorageType}} added in HDFS-11482 is that, currently given
> a node, the method iterates all its children to sum up the number of
> candidate datanodes. Since datanode status change is much less frequent than
> block placement request. It is more efficient to get rid of this iteration
> check, by probably maintaining another disk type counter map. This JIRA
> tracks (but not limited) this optimization.
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