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From "Masatake Iwasaki (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11765) Fix:Performance regression due to incorrect use of DataChecksum
Date Tue, 09 May 2017 00:31:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11765?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16001850#comment-16001850

Masatake Iwasaki commented on HDFS-11765:

The patch lgtm too. I'm running HDFS tests with the patch applied. +1 if there is no failures
except for known flaky ones.

bq. I find that the write performance decreased by 13%

[~GeLiXin], can you share how you did the comparison? It would be nice if we can reproduce
the issue by TestDFSIO or similar.

BlockReceiver seems to be relevant caller of {{DataChecksum#BlockReceiver}} with non-direct
buffer. Based on the result of Crc32PerformanceTest, NativeCrc32 is faster than CRC32 if bytes-per-checksum
<= 128 on my environment.

> Fix:Performance regression due to incorrect use of DataChecksum
> ---------------------------------------------------------------
>                 Key: HDFS-11765
>                 URL: https://issues.apache.org/jira/browse/HDFS-11765
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: native, performance
>    Affects Versions: 2.8.0, 3.0.0-alpha1
>            Reporter: LiXin Ge
>            Assignee: LiXin Ge
>         Attachments: HDFS-11765.patch
> Recently I have upgraded my Hadoop version from 2.6 to 3.0, and I find that the write
performance decreased by 13%. After some days comparative analysis, It's seems introduced
by HADOOP-10865. 
> Since James Thomas have done the work that native checksum can run against byte[] arrays
instead of just against byte buffers, we may use native method preferential because it runs
faster than others.
> [~szetszwo] and [~iwasakims] could you take a look at this to see if  it make bad effect
on your benchmark test? [~tlipcon] could you help to see if I have make mistakes in this patch?
> thanks!

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