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Commit Tag Bot commented on LUCENE-4661: ---------------------------------------- [branch_4x commit] Michael McCandless http://svn.apache.org/viewvc?view=revision&revision=1429617 LUCENE-4661: lower default maxThread/MergeCount in CMS > Reduce default maxMerge/ThreadCount for ConcurrentMergeScheduler > ---------------------------------------------------------------- > > Key: LUCENE-4661 > URL: https://issues.apache.org/jira/browse/LUCENE-4661 > Project: Lucene - Core > Issue Type: Improvement > Reporter: Michael McCandless > Assignee: Michael McCandless > Fix For: 4.1, 5.0 > > > I think our current defaults (maxThreadCount=#cores/2, > maxMergeCount=maxThreadCount+2) are too high ... I've frequently found > merges falling behind and then slowing each other down when I index on > a spinning-magnets drive. > As a test, I indexed all of English Wikipedia with term-vectors (= > heavy on merging), using 6 threads ... at the defaults > (maxThreadCount=3, maxMergeCount=5, for my machine) it took 5288 sec > to index & wait for merges & commit. When I changed to > maxThreadCount=1, maxMergeCount=2, indexing time sped up to 2902 > seconds (45% faster). This is on a spinning-magnets disk... basically > spinning-magnets disk don't handle the concurrent IO well. > Then I tested an OCZ Vertex 3 SSD: at the current defaults it took > 1494 seconds and at maxThreadCount=1, maxMergeCount=2 it took 1795 sec > (20% slower). Net/net the SSD can handle merge concurrency just fine. > I think we should change the defaults: spinning magnet drives are hurt > by the current defaults more than SSDs are helped ... apps that know > their IO system is fast can always increase the merge concurrency. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org