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https://issues.apache.org/jira/browse/LUCENE-1609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12718175#action_12718175
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Michael McCandless commented on LUCENE-1609:
--------------------------------------------
Alas... the big problem with doing this up-front is the
IndexReader.setTermIndexInterval, which relies on the fact that the index is
loaded lazily.
So, maybe we need to wait until 3.0 to do this up-front.
But perhaps for this issue we should make it possible to pass in the
termIndexInterval to IndexReader.open, and deprecate the current methods, and
then in 3.0 we could switch to up-front loading.
> 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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