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https://issues.apache.org/jira/browse/LUCENE-9535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17200160#comment-17200160
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Uwe Schindler commented on LUCENE-9535:
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Michael: Are all your CPU fans OK?
I had this problem on the Policeman Jenkins server. When the temperature goes
up, Linux slows down CPU frequency. Maybe that'Äs happening here, because the
CPU is busy for longer time.
> 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
>
>
> 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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