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Posted to issues@lucene.apache.org by "Michael McCandless (Jira)" <ji...@apache.org> on 2021/05/25 13:56:00 UTC
[jira] [Commented] (LUCENE-9972) Performance regression in
NRTCachingDirectory
[ https://issues.apache.org/jira/browse/LUCENE-9972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17351078#comment-17351078 ]
Michael McCandless commented on LUCENE-9972:
--------------------------------------------
Yeah let's try to find a better solution that doesn't kill performance so much!
LUCENE-9115 fixed a possibly horrific memory leak, since before that fix, {{NRTCachingDirectory}} might cache ginormous files.
If you use the new {{NRTCachingDirectory}}, but tell it it can use infinite RAM (clearly not a safe thing to do in general / in production), does that also get you back to the same original performance?
> Performance regression in NRTCachingDirectory
> ---------------------------------------------
>
> Key: LUCENE-9972
> URL: https://issues.apache.org/jira/browse/LUCENE-9972
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/store
> Affects Versions: 8.8.2
> Reporter: Markus Gietzen
> Priority: Major
> Labels: performance
>
> This issue has been discussed here:
> [http://mail-archives.apache.org/mod_mbox/lucene-java-user/202105.mbox/%3cAM0PR02MB4963712F269C5BF70951F0A3EF2B9@AM0PR02MB4963.eurprd02.prod.outlook.com%3e]
>
> Summary: To get the same speed as in 8.3 I have to overwrite NRTCachingDirectory#doCacheWrite
> in 8.8 with the implementation from 8.3. Otherwise it's magnitudes slower.
>
> It seems that the solution for https://issues.apache.org/jira/browse/LUCENE-9115 increases the number of calls to native-OpenFile (due to falling down to MMAP-Directory) by a very large amount.
> I understand the reasoning behind LUCENE-9115 but in fact it destroys the performance of our product. For now sub-classing NRTCachingDirectory with the old implementation of doCacheWrite() solves the issue but it would be great to have an "offical" solution of course.
>
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