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https://issues.apache.org/jira/browse/LUCENE-4740?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Uwe Schindler updated LUCENE-4740:
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Attachment: LUCENE-4740.patch
Attached you will find the patch, that disables tracking of clones if the
unmapping is disabled. We dont need to make the setting in MMapDirectory
unmodifiable, after changing it all IndexInputs created afterwards, the new
setting is used. This does not differ from the previous behaviour or unmapping
at all.
In general, people should in any case set this setting after constrcution (we
may add a ctor param, too).
> 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
> Reporter: Kristofer Karlsson
> Priority: Critical
> Attachments: 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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