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Date: Mon, 3 Oct 2016 15:42:20 +0000 (UTC)
From: "Shawn Heisey (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
Message-ID: <JIRA.12786211.1427466224000.722048.1475509340757@Atlassian.JIRA>
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References: <JIRA.12786211.1427466224000@Atlassian.JIRA> <JIRA.12786211.1427466224605@arcas>
Subject: [jira] [Commented] (SOLR-7319) Workaround the "Four Month Bug"
 causing GC pause problems
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archived-at: Mon, 03 Oct 2016 15:42:23 -0000


    [ https://issues.apache.org/jira/browse/SOLR-7319?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15542699#comment-15542699 ] 

Shawn Heisey commented on SOLR-7319:
------------------------------------

Sounds like a good plan to me.


> Workaround the "Four Month Bug" causing GC pause problems
> ---------------------------------------------------------
>
>                 Key: SOLR-7319
>                 URL: https://issues.apache.org/jira/browse/SOLR-7319
>             Project: Solr
>          Issue Type: Bug
>          Components: scripts and tools
>    Affects Versions: 5.0
>            Reporter: Shawn Heisey
>            Assignee: Shawn Heisey
>         Attachments: SOLR-7319.patch, SOLR-7319.patch, SOLR-7319.patch
>
>
> A twitter engineer found a bug in the JVM that contributes to GC pause problems:
> http://www.evanjones.ca/jvm-mmap-pause.html
> Problem summary (in case the blog post disappears):  The JVM calculates statistics on things like garbage collection and writes them to a file in the temp directory using MMAP.  If there is a lot of other MMAP write activity, which is precisely how Lucene accomplishes indexing and merging, it can result in a GC pause because the mmap write to the temp file is delayed.
> We should implement the workaround in the solr start scripts (disable creation of the mmap statistics tempfile) and document the impact in CHANGES.txt.


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