[jira] [Commented] (KUDU-1447) Document recommendation to disable THP

["Adar Dembo (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KUDU-1447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15279482#comment-15279482 ] 

Adar Dembo commented on KUDU-1447:
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Are all el6 systems affected? Or was this fixed at some point? I'm asking because you mentioned on Slack that el7 isn't vulnerable to this, so it must have been fixed at some point.

Doesn't this issue negatively affect any application? You may want to file a JIRA against CDH and perhaps CM (to discover this with a host inspection).

> 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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