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https://issues.apache.org/jira/browse/CASSANDRA-7486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14899937#comment-14899937
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Benedict commented on CASSANDRA-7486:
-------------------------------------
bq.
[here is
one|http://cstar.datastax.com/graph?stats=2611ee46-5ee4-11e5-a4e4-42010af0688f&metric=op_rate&operation=1_user&smoothing=1&show_aggregates=true&xmin=0&xmax=9028.03&ymin=0&ymax=146633.3]
10x larger
and another 100x larger [is still
running|http://cstar.datastax.com/tests/id/01b714d8-5f32-11e5-a4e4-42010af0688f]
Interestingly, the completed 10x larger is a more nuanced picture, but this is
because CMS got slower for one of the runs, not G1GC faster - but it never got
up to its prior speed - this is weird, since 2.2 did manage to get up to its
faster speed still, so there may be something funny going on on that particular
test.
bq. It seems that the max heap is still 8G in trunk so maybe it is unfair for
G1. What is the heap size of these tests?
I'm not sure I would call that unfair. These boxes have no more than 64Gb of
RAM, I'm pretty sure (perhaps only 32Gb), and so for anything but the most
write-heavy workloads an 8Gb heap is probably what you'll want to ensure the
file cache can make meaningful contributions to performance. Certainly we can
and should test more scenarios, but this is a pretty typical setup for a pretty
typical piece of hardware. We should consider giving users profiles for
different workloads, though, and consider raising the max heap much higher for
write-heavy workloads, or boxes with gigantic banks of RAM, and use G1
accordingly (as driven by our research)
> Migrate to G1GC by default
> --------------------------
>
> Key: CASSANDRA-7486
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7486
> Project: Cassandra
> Issue Type: New Feature
> Components: Config
> Reporter: Jonathan Ellis
> Fix For: 3.0 alpha 1
>
>
> See
> http://www.slideshare.net/MonicaBeckwith/garbage-first-garbage-collector-g1-7486gc-migration-to-expectations-and-advanced-tuning
> and https://twitter.com/rbranson/status/482113561431265281
> May want to default 2.1 to G1.
> 2.1 is a different animal from 2.0 after moving most of memtables off heap.
> Suspect this will help G1 even more than CMS. (NB this is off by default but
> needs to be part of the test.)
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