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https://issues.apache.org/jira/browse/CASSANDRA-20296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17939676#comment-17939676
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Stefan Miklosovic commented on CASSANDRA-20296:
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follow-up for -XX:MaxDirectMemorySize which was discussed here (1) was
committed in 5.0 and trunk branches here (2)
(1) https://the-asf.slack.com/archives/CK23JSY2K/p1743065084687319
(2)
https://github.com/apache/cassandra/commit/d954c19b21bcf53da3f15fae40a0751c6dcc73df
> Heap and GC jvm flags improvements
> ----------------------------------
>
> Key: CASSANDRA-20296
> URL: https://issues.apache.org/jira/browse/CASSANDRA-20296
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Local/Config
> Reporter: Michael Semb Wever
> Assignee: Michael Semb Wever
> Priority: Normal
> Fix For: 5.0.4, 5.1
>
> Attachments: ci_summary_thelastpickle-mck-20296-5.0_155.html,
> results_details_thelastpickle-mck-20296-5.0_155.tar.xz
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> A few improvements can be made to the configuration files:
> * conf/cassandra-env.sh
> * conf/jvm-server.options
> * conf/jvm11-server.options
> * conf/jvm17-server.options
> G1 can rely on `-XX:G1NewSizePercent=50` to always floor the young
> generation's size to 50% of the heap. (In production this can be raised to
> 66% for optimal performance.)
> Fixing the young generation size with `-Xmn` is only applicable to CMS,
> so move it to the appropriate section.
> When using G1, we can automatically set (the default)
> `-XX:ParallelGCThreads` and `-XX:ConcGCThreads` to the number of system cpu
> cores.
> The auto-generated (default) heap size is now half the server's physical
> RAM, capped at 16G for CMS and 31G for G1.
> Increase MaxTenuringThreshold from 1 to 2, as evidence has shown it has
> no cost (over values of zero or one), but can have significant benefits in
> keeping objects in the young generation. While, values above 2 don't have
> any noticeable benefit.
> Always set CASSANDRA_HEAPDUMP_DIR, default it to $CASSANDRA_LOG_DIR, to
> avoid hprof filling up unexpected disk volumes. Assumption here is that the
> logs directory is large enough to handle these dumps, and/or operators are
> monitoring these directories more than other randon/unknown directories.
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