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From "Aaron T. Myers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3796) Speed up edit log tests by avoiding fsync()
Date Wed, 15 Aug 2012 15:52:37 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13435225#comment-13435225
] 

Aaron T. Myers commented on HDFS-3796:
--------------------------------------

+1, the patch looks good to me.
                
> Speed up edit log tests by avoiding fsync()
> -------------------------------------------
>
>                 Key: HDFS-3796
>                 URL: https://issues.apache.org/jira/browse/HDFS-3796
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: test
>    Affects Versions: 3.0.0, 2.2.0-alpha
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>         Attachments: hdfs-3796.txt, hdfs-3796.txt
>
>
> Our edit log tests are very slow because they incur a lot of fsyncs as they write out
transactions. Since fsync() has no effect except in the case of power outages or system crashes,
and we don't care about power outages in the context of tests, we can safely skip the fsync
without any loss in coverage.
> In my tests, this sped up TestEditLog by about 5x. The testFuzzSequences test case improved
from ~83 seconds with fsync to about 5 seconds without. These results are from my SSD laptop
- they are probably even more drastic on spinning media.

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