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https://issues.apache.org/jira/browse/CASSANDRA-20129?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Caleb Rackliffe updated CASSANDRA-20129:
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Status: Ready to Commit (was: Review In Progress)
> Restore optimization in MultiCBuilder around building one clustering
> --------------------------------------------------------------------
>
> Key: CASSANDRA-20129
> URL: https://issues.apache.org/jira/browse/CASSANDRA-20129
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Legacy/Local Write-Read Paths
> Reporter: Caleb Rackliffe
> Assignee: Caleb Rackliffe
> Priority: Normal
> Fix For: 5.x
>
> Attachments: 41 BTree builder inits.png, 41 vs trunk GC.png, 41 vs
> trunk TLAB allocations.png, ci_summary.html, post-patch-allocations-2.jfr,
> pre-patch-allocations.jfr, trunk BTree builder inits.png
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Back in CASSANDRA-10409, we optimized the single clustering case for
> {{MultiCBuilder}} to produce less garbage. In CASSANDRA-19341, we de-facto
> removed that optimization, and I'm seeing increased allocations in trunk,
> specifically at least double the number of {{BTree}} builders. In the
> write-heavy workload I'm profiling, this jumps up to become the most common
> TLAB allocation. I'm attaching JFR screenshots from 4.1 and trunk that show
> the codepaths that touch this on both versions. We should consider
> reintroducing something like the old {{OneClusteringBuilder}}.
> I used {{WriteBench}} to explore things here, mostly w/ the TRUNCATE
> {{EndOp}}, and made sure commitlog writes, view updates, and
> {{CassandraTableWriteHandler}} tracing were disabled to reduce the noise.
>
> [~blerer]
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