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https://issues.apache.org/jira/browse/CASSANDRA-14261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16383189#comment-16383189
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Jeff Jirsa commented on CASSANDRA-14261:
----------------------------------------
So I've re-run my trivial tests on a laptop just to demonstrate where the
improvement lies, and the good thing is it repro's easily and consistently,
which reinforces that it's real gain.
While I was there, I remembered that I had also cleaned up one additional check
(isCounter() was checking instanceof for thrift, and with thrift removed, I
believe this can be removed), which helps a bit more.
Squashed patch here
[https://github.com/jeffjirsa/cassandra/commit/d627dfbb3a7653d8c5a8c7a170a9621edbc1f1cd]
Here's the top threads with trunk:
!unpatched-hot-threads-top.png|height=400,width=800!
And expanded down to see the isDroppedColumn time:
!unpatched-hot-threads.png|height=400,width=800!
And the trunk tlab allocation during this compaction test:
!unpatched-tlab.png|height=400,width=800!
After applying these patches (except the isCounter() patch, which I did after
this run, note that BTreeBuilder.resolve() has fallen significantly (as
isDroppedColumn become trivially cheap):
!patched-hot-threads.png|height=400,width=800!
And tlab allocation (note we've done the same compaction, but allocated 500MB
fewer empty iterators):
!patched-tlab.png|height=400,width=800!
> Compaction Profiling Improvements
> ---------------------------------
>
> Key: CASSANDRA-14261
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14261
> Project: Cassandra
> Issue Type: Improvement
> Components: Compaction
> Reporter: Jeff Jirsa
> Assignee: Jeff Jirsa
> Priority: Minor
> Fix For: 4.x
>
> Attachments: patched-hot-threads.png, patched-tlab.png,
> unpatched-hot-threads-top.png, unpatched-hot-threads.png, unpatched-tlab.png
>
>
> There's some low hanging fruit in some laptop compaction runs, such as
> creating a ton of the same object unnecessarily and hashing cell names
> repeatedly to see if a column is dropped even when we should know that the
> table has no dropped columns.
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