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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7486) Compare CMS and G1 pause times
Date Fri, 01 May 2015 18:41:10 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14523630#comment-14523630
] 

Ariel Weisberg commented on CASSANDRA-7486:
-------------------------------------------

bq. ^ G1 doesn't work that way.
I am talking about CMS. When I looked at the 12 gigabyte heap the old gen grew to 4.1 gigabytes
and I didn't see any point that it shrunk.

bq.  I'm spending all of my time tuning users' clusters where the #1 first issue every time
is getting CMS to behave.
We can make the case for G1 in different ways. If we want to do it based on real world results
that is fine with me.

To Benedict's point I think looking at all the operations we care about on realistic time
scales is something we would have to do to really know what the differences are. I wish we
had this stuff in CI so it would just be a matter of changing the flags, but we aren't there
yet.

> Compare CMS and G1 pause times
> ------------------------------
>
>                 Key: CASSANDRA-7486
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7486
>             Project: Cassandra
>          Issue Type: Test
>          Components: Config
>            Reporter: Jonathan Ellis
>            Assignee: Shawn Kumar
>             Fix For: 2.1.x
>
>
> 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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