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https://issues.apache.org/jira/browse/SPARK-3570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14317495#comment-14317495
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Apache Spark commented on SPARK-3570:
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User 'kayousterhout' has created a pull request for this issue:
https://github.com/apache/spark/pull/4550
> Shuffle write time does not include time to open shuffle files
> --------------------------------------------------------------
>
> Key: SPARK-3570
> URL: https://issues.apache.org/jira/browse/SPARK-3570
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 0.9.2, 1.0.2, 1.1.0
> Reporter: Kay Ousterhout
> Assignee: Kay Ousterhout
> Attachments: 3a_1410854905_0_job_log_waterfall.pdf,
> 3a_1410957857_0_job_log_waterfall.pdf
>
>
> Currently, the reported shuffle write time does not include time to open the
> shuffle files. This time can be very significant when the disk is highly
> utilized and many shuffle files exist on the machine (I'm not sure how severe
> this is in 1.0 onward -- since shuffle files are automatically deleted, this
> may be less of an issue because there are fewer old files sitting around).
> In experiments I did, in extreme cases, adding the time to open files can
> increase the shuffle write time from 5ms (of a 2 second task) to 1 second.
> We should fix this for better performance debugging.
> Thanks [~shivaram] for helping to diagnose this problem. cc [~pwendell]
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