lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Kristofer Karlsson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4740) Weak references cause extreme GC churn
Date Thu, 31 Jan 2013 15:55:12 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4740?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13567734#comment-13567734
] 

Kristofer Karlsson commented on LUCENE-4740:
--------------------------------------------

I am not sure if this is a problem in practice, but there are also WeakIdentityMaps used in
AttributeImpl, AttributeSource, VirtualMethod where the keys of the map are classes, which
I don't imagine get allocated or collected a lot at all.

I replaced those maps with regular ConcurrentHashMap<Class, X> without any negative
impact.
                
> 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/index
>    Affects Versions: 3.6.1
>         Environment: Linux debian squeeze 64 bit, Oracle JDK 6, 32 GB RAM, 16 cores
>            Reporter: Kristofer Karlsson
>            Priority: Critical
>
> 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.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org


Mime
View raw message