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https://issues.apache.org/jira/browse/LUCENE-1609?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dan Rosher updated LUCENE-1609:
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    Attachment: LUCENE-1609.patch

I've added the TermInfosReader object to the constructor of the IndexNotRead 
object so that it can be synchronised  on during readIndex, and then protect 
indexTerms, indexInfos, indexPointer

> 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
>             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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