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https://issues.apache.org/jira/browse/HADOOP-7714?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13121705#comment-13121705
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Todd Lipcon commented on HADOOP-7714:
-------------------------------------
Thanks for the comments. I'm doing some more refactoring of the readahead code,
and integrating it into parts of the shuffle as well as an experiment. Running
a terasort, my current iteration of the patch slowed down the map phase by a
few percent, but really improved speed of the reduce phase (I'm running untuned
settings so the reduce phase has lots of IFile merges, which I've plugged
readahead into). The good news is the total runtime for my terasort went from
40m13s to 33m7s (near 20% speedup). The reduce phase (counting from when mapper
output read 100% on my console) went from about 19 minutes down to 9 minutes.
It might be that the map phase slowed down due to the bug you found above. Let
me look into that and run some more experiments - then I'll post another patch.
> Add support in native libs for OS buffer cache management
> ---------------------------------------------------------
>
> Key: HADOOP-7714
> URL: https://issues.apache.org/jira/browse/HADOOP-7714
> Project: Hadoop Common
> Issue Type: Bug
> Components: native
> Affects Versions: 0.24.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Attachments: 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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