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https://issues.apache.org/jira/browse/KUDU-1447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16200016#comment-16200016
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Todd Lipcon commented on KUDU-1447:
-----------------------------------
Been chasing slow thread startup times again this week and found a good smoking
gun on this issue. Found a trace using perf which shows an mmap() call taking
1.56 seconds. Meanwhile khugepaged is burning plenty of cycles in 'copy_page_c'
etc.
> Document recommendation to disable THP
> --------------------------------------
>
> Key: KUDU-1447
> URL: https://issues.apache.org/jira/browse/KUDU-1447
> Project: Kudu
> Issue Type: Improvement
> Components: documentation
> Affects Versions: 0.8.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
>
> Doing a bunch of cluster testing, I finally got to the root of why sometimes
> threads take several seconds to start up, causing various timeout issues,
> false elections, etc. It turns out that khugepaged does synchronous page
> compaction while holding a process's mmap semaphore, and when that's
> concurrent with lots of IO, can block for several seconds.
> https://lkml.org/lkml/2011/7/26/103
> To avoid this, we should tell users to set hugepages to "madvise" or "never"
> -- it's not sufficient to just disable defrag, because khugepaged still runs
> in the background in that case and causes this sporadic issue.
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