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Benedict Elliott Smith commented on CASSANDRA-15388:
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bq. Given the size of the jmh patch though, I’d lean towards reviewing it
separately.
Sure, I can feel a follow-up JIRA
bq. What's the compilation breakage you’re seeing?
If you set {{AGENT_MEASUREMENT = false}}, you need
[this|https://github.com/belliottsmith/cassandra/commit/1a5cfea508285255eea8927b5ea5ad596c405151#diff-5d25f445e825fbeef166372877b810d1R150]
> Add compaction allocation measurement test to support compaction gc
> optimization.
> ----------------------------------------------------------------------------------
>
> Key: CASSANDRA-15388
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15388
> Project: Cassandra
> Issue Type: Sub-task
> Components: Local/Compaction
> Reporter: Blake Eggleston
> Assignee: Blake Eggleston
> Priority: Normal
> Fix For: 4.0
>
>
> This adds a test that is able to quickly and accurately measure the effect of
> potential gc optimizations against a wide range of (synthetic) compaction
> workloads. This test accurately measures allocation rates from 16 workloads
> in less that 2 minutes.
> This test uses google’s {{java-allocation-instrumenter}} agent to measure the
> workloads. Measurements using this agent are very accurate and pretty
> repeatable from run to run, with most variance being negligible (1-2 bytes
> per partition), although workloads with larger but fewer partitions vary a
> bit more (still less that 0.03%).
> The thinking behind this patch is that with compaction, we’re generally
> interested in the memory allocated per partition, since garbage scales more
> or less linearly with the number of partitions compacted. So measuring
> allocation from a small number of partitions that otherwise represent real
> world use cases is a good enough approximation.
> In addition to helping with compaction optimizations, this test could be used
> as a template for future optimization work. This pattern could also be used
> to set allocation limits on workloads/operations and fail CI if the
> allocation behavior changes past some threshold.
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