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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (LUCENE-4740) Weak references cause extreme GC churn
Date Sat, 02 Feb 2013 10:46:13 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4740?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13569498#comment-13569498
] 

Uwe Schindler edited comment on LUCENE-4740 at 2/2/13 10:44 AM:
----------------------------------------------------------------

I committed this to trunk and 4.x branch.

It is not yet planned to release another 3.6.x version. Users should upgrade to Lucene 4.x
(4.2 will contain this patch).

                
      was (Author: thetaphi):
    I committed this to trunk and 4.x branch.

It is not yet planned to release another 3.6.x version. Users should upgrade to Lucene 4.x
(4.x will contain this patch).

                  
> Weak references cause extreme GC churn
> --------------------------------------
>
>                 Key: LUCENE-4740
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4740
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: core/store
>    Affects Versions: 3.6.1
>         Environment: Linux debian squeeze 64 bit, Oracle JDK 6, 32 GB RAM, 16 cores
> -Xmx16G
>            Reporter: Kristofer Karlsson
>             Fix For: 4.2, 5.0
>
>         Attachments: LUCENE-4740.patch, LUCENE-4740.patch
>
>
> We are running a set of independent search machines, running our custom software using
lucene as a search library. We recently upgraded from lucene 3.0.3 to 3.6.1 and noticed a
severe degradation of performance.
> After doing some heap dump digging, it turns out the process is stalling because it's
spending so much time in GC. We noticed about 212 million WeakReference, originating from
WeakIdentityMap, originating from MMapIndexInput.
> Our problem completely went away after removing the clones weakhashmap from MMapIndexInput,
and as a side-effect, disabling support for explictly unmapping the mmapped data.

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