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From "Simon Willnauer (Commented) (JIRA)" <>
Subject [jira] [Commented] (LUCENE-3653) Lucene Search not scalling
Date Thu, 22 Dec 2011 10:36:31 GMT


Simon Willnauer commented on LUCENE-3653:

bq. Hi Simon, for 3.x I agree. In trunk we already have no synchronization at all (committed
2 days ago; improved yesterday: LUCENE-3631), so there is no need to change anything.
uwe that patch is against 3.x - I didn't intend to apply this to 4.0 since we do totally different
things there. I will commit this if nobody objects in a bit.
> Lucene Search not scalling
> --------------------------
>                 Key: LUCENE-3653
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Gerrit Jansen van Vuuren
>         Attachments:, LUCENE-3653-VirtualMethod+AttributeSource.patch, LUCENE-3653-VirtualMethod+AttributeSource.patch,
LUCENE-3653-VirtualMethod+AttributeSource.patch, LUCENE-3653-no-sync.png, LUCENE-3653-sync-.png,
LUCENE-3653.patch, LUCENE-3653.patch, LUCENE-3653.patch-BiasedLockingStartupDelay_1.png, LUCENE-3653.patch-BiasedLockingStartupDelay_2.png,
LUCENE-3653.patch-BiasedLockingStartupDelay_3.png, Threads-LUCENE-3653.patch.png, 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,
> 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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