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https://issues.apache.org/jira/browse/LUCENE-1609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12716376#action_12716376
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Yonik Seeley commented on LUCENE-1609:
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It would be nice to fix, but I wonder how important it is (i.e. a must fix for
2.9 vs 3.0 where we can use Java5)
Wouldn't an application that hit contention on this very fast test, simply go
on to hit a different contention point after this one is removed?
A much better application fix is to simply limit the number of threads
executing queries.
> Eliminate synchronization contention on initial index reading in
> TermInfosReader ensureIndexIsRead
> ---------------------------------------------------------------------------------------------------
>
> Key: LUCENE-1609
> URL: https://issues.apache.org/jira/browse/LUCENE-1609
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: 2.9
> Environment: Solr
> Tomcat 5.5
> Ubuntu 2.6.20-17-generic
> Intel(R) Pentium(R) 4 CPU 2.80GHz, 2Gb RAM
> Reporter: Dan Rosher
> Assignee: Michael McCandless
> Fix For: 2.9
>
> Attachments: LUCENE-1609.patch, LUCENE-1609.patch
>
>
> synchronized method ensureIndexIsRead in TermInfosReader causes contention
> under heavy load
> Simple to reproduce: e.g. Under Solr, with all caches turned off, do a simple
> range search e.g. id:[0 TO 999999] on even a small index (in my case 28K
> docs) and under a load/stress test application, and later, examining the
> Thread dump (kill -3) , many threads are blocked on 'waiting for monitor
> entry' to this method.
> Rather than using Double-Checked Locking which is known to have issues, this
> implementation uses a state pattern, where only one thread can move the
> object from IndexNotRead state to IndexRead, and in doing so alters the
> objects behavior, i.e. once the index is loaded, the index nolonger needs a
> synchronized method.
> In my particular test, this uncreased throughput at least 30 times.
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