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https://issues.apache.org/jira/browse/HADOOP-2172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12541290
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Johan Oskarsson commented on HADOOP-2172:
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If the cache is moved to local filesystem only I assume the dfs and other
filesystems have a similar cache? Or do they not need one?
Performance with either of these three patches are pretty much identical for me
so my only concern is what happens with other filesystems.
> PositionCache was removed from FSDataInputStream, causes extremely bad
> MapFile performance
> ------------------------------------------------------------------------------------------
>
> Key: HADOOP-2172
> URL: https://issues.apache.org/jira/browse/HADOOP-2172
> Project: Hadoop
> Issue Type: Bug
> Components: fs
> Affects Versions: 0.14.3, 0.15.0
> Reporter: Johan Oskarsson
> Assignee: Johan Oskarsson
> Priority: Blocker
> Fix For: 0.15.1
>
> Attachments: HADOOP-2172-2.patch, HADOOP-2172-3.patch,
> positioncache-v1.patch
>
>
> The PositionCache in FSDataInputStream seems to have been removed in
> HADOOP-1470. This causes for example MapFile.get usage to be extremely slow
> as the file position isn't cached in memory.
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