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https://issues.apache.org/jira/browse/HADOOP-12975?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15241536#comment-15241536
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Elliott Clark commented on HADOOP-12975:
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bq. What motivates choosing 50% of the full refresh period as the jitter
default?
50% is probably too high, I'll change it to 15%.
But a percentage is chosen as it makes the jitter scale with anyone who changes
du periods. If it's a set number then someone with a refresh period of days
won't get any benefit from the jitter.
> Add jitter to DU's thread
> -------------------------
>
> Key: HADOOP-12975
> URL: https://issues.apache.org/jira/browse/HADOOP-12975
> Project: Hadoop Common
> Issue Type: Sub-task
> Reporter: Elliott Clark
> Assignee: Elliott Clark
> Attachments: HADOOP-12975v0.patch, HADOOP-12975v1.patch
>
>
> Running DU across lots of disks is very expensive and running all of the
> processes at the same time creates a noticeable IO spike. We should add some
> jitter.
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