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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7832) Using mincore to understand the effect of fadvise in the Linux page cache
Date Thu, 17 Nov 2011 21:35:51 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13152351#comment-13152351
] 

Todd Lipcon commented on HADOOP-7832:
-------------------------------------

btw, another thing I think would be very interesting to look at: count the percentage of write/flush
calls on the DN that take longer than ~10ms. This would serve to separate non-blocking writes
(that just dirty pages) from blocking writes (once the max dirty page ratio has been exceeded
(/proc/sys/vm/dirty_ratio)). Would be very interested to see if the sync_file_range calls
improve this metric. (again it's a theory but not something I've verified)
                
> 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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