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From "Simon Willnauer (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3653) Lucene Search not scalling
Date Mon, 19 Dec 2011 08:52:30 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3653?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13172111#comment-13172111
] 

Simon Willnauer commented on LUCENE-3653:
-----------------------------------------

Gerrit, before I spend time on fixing this single IMO likely uncontented lock in org.apache.lucene.index.SegmentCoreReaders.getTermsReader()
can I ask you to run your tests / benchmarks with -XX:BiasedLockingStartupDelay=0 as far as
I can see you are running micro benchmarks which start up very quickly. Locks accessed right
after startup behave differently in the JVM than other locks ie. sync blocks. Can you retest
and report back?

simon
                
> Lucene Search not scalling
> --------------------------
>
>                 Key: LUCENE-3653
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3653
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Gerrit Jansen van Vuuren
>         Attachments: App.java, LUCENE-3653-VirtualMethod+AttributeSource.patch, LUCENE-3653-VirtualMethod+AttributeSource.patch,
LUCENE-3653-VirtualMethod+AttributeSource.patch, lucene-unsync.diff, profile_1_a.png, profile_1_b.png,
profile_1_c.png, profile_1_d.png, profile_2_a.png, profile_2_b.png, profile_2_c.png
>
>
> I've noticed that when doing thousands of searches in a single thread the average time
is quite low i.e. a few milliseconds. When adding more concurrent searches doing exactly the
same search the average time increases drastically. 
> I've profiled the search classes and found that the whole of lucene blocks on 
> org.apache.lucene.index.SegmentCoreReaders.getTermsReader
> org.apache.lucene.util.VirtualMethod
>   public synchronized int getImplementationDistance 
> org.apache.lucene.util.AttributeSourcew.getAttributeInterfaces
> These cause search times to increase from a few milliseconds to up to 2 seconds when
doing 500 concurrent searches on the same in memory index. Note: That the index is not being
updates at all, so not refresh methods are called at any stage.
> Some questions:
>   Why do we need synchronization here?
>   There must be a non-lockable solution for these, they basically cause lucene to be
ok for single thread applications but disastrous for any concurrent implementation.
> I'll do some experiments by removing the synchronization from the methods of these classes.

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