[jira] Commented: (LUCENE-1322) Remove synchronization in CompoundFileReader

["robert engels (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-1322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609235#action_12609235 ] 

robert engels commented on LUCENE-1322:
---------------------------------------

This comment is very misleading.

Since there is IO involved, any operation can block, which will lower CPU utilization.

You just need to make sure that the locks control different physical resources.

> Remove synchronization in CompoundFileReader
> --------------------------------------------
>
>                 Key: LUCENE-1322
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1322
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.3.1
>            Reporter: Jason Rutherglen
>            Priority: Trivial
>
> Currently there is what seems to be unnecessary synchronization in CompoundFileReader.  This is solved by cloning the base IndexInput.  Synchronization in low level IO classes creates lock contention on highly multi threaded Lucene installations, so much so that in many cases the CPU utilization never reaches the maximum without using something like ParallelMultiSearcher.

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