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https://issues.apache.org/jira/browse/LUCENE-9535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17201010#comment-17201010
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ASF subversion and git services commented on LUCENE-9535:
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Commit d226abd4481a5bd837264a7c53d1b13f417842ad in lucene-solr's branch
refs/heads/master from Adrien Grand
[ https://gitbox.apache.org/repos/asf?p=lucene-solr.git;h=d226abd ]
LUCENE-9535: Make ByteBuffersDataOutput#ramBytesUsed run in constant-time.
(#1917)
> Investigate recent indexing slowdown for wikimedium documents
> -------------------------------------------------------------
>
> Key: LUCENE-9535
> URL: https://issues.apache.org/jira/browse/LUCENE-9535
> Project: Lucene - Core
> Issue Type: Task
> Reporter: Adrien Grand
> Priority: Minor
> Attachments: cpu_profile.svg
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Nightly benchmarks report a ~10% slowdown for 1kB documents as of September
> 9th: [http://people.apache.org/~mikemccand/lucenebench/indexing.html].
> On that day, we added stored fields in DWPT accounting (LUCENE-9511), so I
> first thought this could be due to smaller flushed segments and more merging,
> but I still wonder whether there's something else. The benchmark runs with
> 8GB of heap, 2GB of RAM buffer and 36 indexing threads. So it's about 2GB/36
> = 57MB of RAM buffer per thread in the worst-case scenario that all DWPTs get
> full at the same time. Stored fields account for about 0.7MB of memory, or 1%
> of the indexing buffer size. How can a 1% reduction of buffering capacity
> explain a 10% indexing slowdown? I looked into this further by running
> indexing benchmarks locally with 8 indexing threads and 128MB of indexing
> buffer memory, which would make this issue even more apparent if the smaller
> RAM buffer was the cause, but I'm not seeing a regression and actually I'm
> seeing similar number of flushes when I disabled memory accounting for stored
> fields.
> I ran indexing under a profiler to see whether something else could cause
> this slowdown, e.g. slow implementations of ramBytesUsed on stored fields
> writers, but nothing surprising showed up and the profile looked just like I
> would have expected.
> Another question I have is why the 4kB benchmark is not affected at all.
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