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From "Igor Dvorzhak (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15124) Slow FileSystem.Statistics counters
Date Sun, 17 Dec 2017 17:29:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16294241#comment-16294241

Igor Dvorzhak commented on HADOOP-15124:

I have created PR (https://github.com/apache/hadoop/pull/316) with Draft changes that I have
tested and posted results in the description.

Please, take a look if it looks reasonable and I will clean up it (especially tests) and made
necessary changes so it could be submitted upstream.

> Slow FileSystem.Statistics counters 
> ------------------------------------
>                 Key: HADOOP-15124
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15124
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: common
>    Affects Versions: 2.9.0, 2.8.3, 2.7.5, 3.0.0
>            Reporter: Igor Dvorzhak
> While profiling 1TB TeraGen on Hadoop 2.8.2 cluster (Google Dataproc, 2 workers, GCS
connector) I saw that FileSystem.Statistics code paths Wall time is 5.58% and CPU time is
26.5% of total execution time.
> After switching FileSystem.Statistics implementation to LongAdder consumed Wall time
decreased to 0.006% and CPU time to 0.104% of total execution time.
> Total runtime decreased from 66 mins to 61 mins.
> These results are not conclusive, because I didn't benchmark multiple times to average
results, but regardless of performance gains switching to LongAdder simplifies code and reduces
its complexity.

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