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https://issues.apache.org/jira/browse/CASSANDRA-10403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14938223#comment-14938223
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Jonathan Shook commented on CASSANDRA-10403:
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[~JoshuaMcKenzie] I'd prefer not to make too many assumptions about
confirmation or (human) memory bias on this. We will not get off this carousel
without actual data. However, to the degree that you are right about it, it
should encourage us to explore further, not less. CMS's pain in those cases has
much to do with its inability to scale with hardware sizing and concurrency
trends, which we seem to be working really hard to disregard. Until someone
puts together a view of current and emerging system parameters, we really don't
have the data that we need to set a default.
I posit that the general case system is much bigger in practice that in the
past. I also posit that on those systems, G1 is an obviously better default
than CMS. So, we are likely going to get some data on 1) what the hardware data
looks like in the field and 2) whether or not we can demonstrate the CMS
improvements with larger memory that we've seen with *actual workloads* on
*current system profiles*. I'm simply eager to see more data at this point.
This is a bit out of scope of the ticket, but it is important. If we were able
to set a default depending on the available memory, there would not be a single
default. Trying to scale GC bandwidth up on bigger metal with CMS is arguably
more painful than trying to make G1 useable with lower memory. However, we
don't have to make that bargain as either-or. We can have the best of both, if
we simply align the GC settings to the type of hardware that they work well for.
I'll create another ticket for that.
> Consider reverting to CMS GC on 3.0
> -----------------------------------
>
> Key: CASSANDRA-10403
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10403
> 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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