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From "Jonathan Shook (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-10403) Consider reverting to CMS GC on 3.0
Date Wed, 30 Sep 2015 00:38:04 GMT


Jonathan Shook commented on CASSANDRA-10403:

I do think it is valid, however I expect the findings to be slightly different. The promise
of G1 on smaller systems is more robust performance across a range of workloads without manual
tuning. That said, it probably won't perform as well in terms of ops/s, etc. The question
to me is really whether we are trying to save people from the pain of not going fast enough
or whether we are trying to save them from the pain of a CMS once they start having cascading
IO and heap pressure through the system. I am very curious about our tests proving this out
as we would expect.

As an operator and a developer, I'd take an easily tuned and stable setting over one that
goes fast until it doesn't go, any day. However, some will have already adjusted their cluster
sizing around one expectation, so we'd want to make sure to avoid surprises. With 3.0 having
other changes as well to offset, it might be a wash.

Raw performance is only part of the picture. I would like to see your results, for sure.

> Consider reverting to CMS GC on 3.0
> -----------------------------------
>                 Key: CASSANDRA-10403
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Config
>            Reporter: Joshua McKenzie
>            Assignee: Paulo Motta
>             Fix For: 3.0.0 rc2
> Reference discussion on CASSANDRA-7486.
> For smaller heap sizes G1 appears to have some throughput/latency issues when compared
to CMS. With our default max heap size at 8G on 3.0, there's a strong argument to be made
for having CMS as the default for the 3.0 release.

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