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https://issues.apache.org/jira/browse/HADOOP-10048?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15300600#comment-15300600
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Junping Du commented on HADOOP-10048:
-------------------------------------
Thanks [~jlowe] for updating the patch!
005 patch looks good in overall. Just two minor issues:
{noformat}
+ ctx.dirNumLastAccessed = dirNum;
{noformat}
Given the ctx could be local context, I think we want to update it to the
currentContext which can accessed immediately - something like:
currentContext.get().dirNumLastAccessed = dirNum. Isn't it?
{noformat}
+ if(ctx.localFS.mkdirs(tmpDir)|| ctx.localFS.exists(tmpDir)) {
{noformat}
Shouldn't we check dir exists first then mkdir if not?
> LocalDirAllocator should avoid holding locks while accessing the filesystem
> ---------------------------------------------------------------------------
>
> Key: HADOOP-10048
> URL: https://issues.apache.org/jira/browse/HADOOP-10048
> Project: Hadoop Common
> Issue Type: Improvement
> Affects Versions: 2.3.0
> Reporter: Jason Lowe
> Assignee: Jason Lowe
> Attachments: HADOOP-10048.003.patch, HADOOP-10048.004.patch,
> HADOOP-10048.005.patch, HADOOP-10048.patch, HADOOP-10048.trunk.patch
>
>
> As noted in MAPREDUCE-5584 and HADOOP-7016, LocalDirAllocator can be a
> bottleneck for multithreaded setups like the ShuffleHandler. We should
> consider moving to a lockless design or minimizing the critical sections to a
> very small amount of time that does not involve I/O operations.
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