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From "Andrew Purtell (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7714) Umbrella for usage of native calls to manage OS cache and readahead
Date Tue, 25 Oct 2011 14:42:32 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7714?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13135104#comment-13135104
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Andrew Purtell commented on HADOOP-7714:
----------------------------------------

This issue is 95% of the way toward a tuning guide for HDFS installs. Perhaps the remaining
5%? @Scott?
                
> Umbrella for usage of native calls to manage OS cache and readahead
> -------------------------------------------------------------------
>
>                 Key: HADOOP-7714
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7714
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: io, native, performance
>    Affects Versions: 0.24.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: graphs.pdf, hadoop-7714-2.txt, hadoop-7714-20s-prelim.txt
>
>
> Especially in shared HBase/MR situations, management of the OS buffer cache is important.
Currently, running a big MR job will evict all of HBase's hot data from cache, causing HBase
performance to really suffer. However, caching of the MR input/output is rarely useful, since
the datasets tend to be larger than cache and not re-read often enough that the cache is used.
Having access to the native calls {{posix_fadvise}} and {{sync_data_range}} on platforms where
they are supported would allow us to do a better job of managing this cache.

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