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Posted to dev@lucene.apache.org by "Michael McCandless (JIRA)" <ji...@apache.org> on 2012/10/08 18:56:02 UTC
[jira] [Commented] (LUCENE-4462) Publishing flushed segments is
single threaded and too costly
[ https://issues.apache.org/jira/browse/LUCENE-4462?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13471662#comment-13471662 ]
Michael McCandless commented on LUCENE-4462:
--------------------------------------------
Patch looks good, thanks Simon!
I think we should keep the safety in there (the fallback to forcePurge if too many segments are backlogged)...? Hopefully it never needs to run... but just in case.
> Publishing flushed segments is single threaded and too costly
> -------------------------------------------------------------
>
> Key: LUCENE-4462
> URL: https://issues.apache.org/jira/browse/LUCENE-4462
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Michael McCandless
> Assignee: Simon Willnauer
> Attachments: LUCENE-4462.patch
>
>
> Spinoff from http://lucene.markmail.org/thread/4li6bbomru35qn7w
> The new TestBagOfPostings failed the build because it timed out after 2 hours ... but in digging I found that it was a starvation issue: the 4 threads were flushing segments much faster than the 1 thread could publish them.
> I think this is because publishing segments (DocumentsWriter.publishFlushedSegment) is actually rather costly (creates CFS file if necessary, writes .si, etc.).
> I committed a workaround for now, to prevent starvation (see svn diff -c 1394704 https://svn.apache.org/repos/asf/lucene/dev/trunk), but we really should address the root cause by moving these costly ops into flush() so that publishing is a low cost operation.
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