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https://issues.apache.org/jira/browse/LUCENE-3653?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171742#comment-13171742
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Gerrit Jansen van Vuuren commented on LUCENE-3653:
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Thanks, I'll keep an eye on the things happening in the trunk.
Creating a Single Tokenizer does help, but the thread blocking still happens
because of the synchronization used in several classes.
I've made some quick changes during the last few days on 3.5, and have included
the diff. (this is not an svn duff sorry).
I agree, if anybody has to decide between, concurrency or storing things twice
then concurrency wins, eventually all the cache data will be available to all
threads, and the overhead goes away. But with synchronization the overhead
never goes away.
Some other points of contention are:
RAMFile : all methods are synchronized.
RAMInputStream: clone()
This method came up during the profiling allot. I changed it from
calling clone to: just create an new instance directly.
I'll try to cleanup some of the code and add a better diff.
> 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-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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