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https://issues.apache.org/jira/browse/HADOOP-7832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13155935#comment-13155935
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Nathan Roberts commented on HADOOP-7832:
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bq. On clusters with lots of blocks, we see block reports taking many minutes
to generate (and incurring lots of seeks) because the FS metadata gets evicted
when MR jobs run.
Todd, have you experimented with /proc/sys/vm/vfs_cache_pressure to deal with
this? Seems like datanodes might want to have this value set very low so that
dentry/inode caches are significantly stickier than page cache pages. I'm
having a hard time coming up with scenarios where this would be detrimental.
> Using mincore to understand the effect of fadvise in the Linux page cache
> -------------------------------------------------------------------------
>
> Key: HADOOP-7832
> URL: https://issues.apache.org/jira/browse/HADOOP-7832
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: io, native, performance
> Reporter: Cristina L. Abad
> Priority: Minor
> Attachments: hadoop-7714-20s-205-mincore.txt
>
>
> This Jira adds a way to log the percentage of pages of a file that were on
> the Linux page cache (when the file is being opened) with the purpose of
> measuring the effect of issuing posix_fadvise (POSIX_FADV_DONTNEED) calls.
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