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https://issues.apache.org/jira/browse/LUCENE-3653?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13172578#comment-13172578
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DM Smith edited comment on LUCENE-3653 at 12/19/11 8:24 PM:
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bq. In fact we were talking here about searching not indexing. It makes no
sense to clone a huge RAM directory from disk to heap and run searches on it.
I saw that this issue is on searching not indexing. I didn't mean to try to
hijack it. I was responding to the statement that RAMDirectory going away (BTW,
the statement on optimize does not regard a search feature but an index one).
I'll have to test to see if the same index problem still is around.
Regarding MMap, there is an open issue with it on Windows: Lucene-1669.
was (Author: dmsmith):
bq. In fact we were talking here about searching not indexing. It makes no
sense to clone a huge RAM directory from disk to heap and run searches on it.
I saw that this issue is on searching not indexing. I didn't mean to try to
hijack it. I was responding to the statement that RAMDirectory going away (BTW,
the statement on optimize does not regard a search feature but an index one). I
still think there is a use case for it in indexing.
Regarding MMap, there is an open issue with it on Windows: Lucene-1669.
> 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-3653-no-sync.png,
> LUCENE-3653-sync-.png, 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, 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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