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https://issues.apache.org/jira/browse/CASSANDRA-7486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14519604#comment-14519604
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Phil Yang edited comment on CASSANDRA-7486 at 4/29/15 3:51 PM:
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I think the default option should be prudently and carefully enough to change.
Usually for C* users, it is acceptable that there is no better performance in
new version. However, it may be unacceptable if the new version get a worse
performance. If there is risk that in some cases G1 is worse than CMS, it may
be a better choice to make G1 an optional choice first by offering another
conf/cassandra-env-g1.sh file to let people have a try and don't change the
default settings.
For the tests comparing G1 and CMS, does the tests cover some extreme case? For
example: bootstrap/rebuild/remove node, repair, lots of queries over
tombstone_failure_threshold... And I think each test should take at lease 24
hours to have several full GCs to estimate the latency.
Furthermore, now using CMS, we have a max heap size (8GB) limit even if the
memory of this node is very large. If we decide to change the default gc
algorithm, what is the suitable new limit?
was (Author: yangzhe1991):
I think the default option should be prudence and care enough to change.
Usually for C* users, it is acceptable that there is no better performance in
new version. However, it may be unacceptable if the new version get a worse
performance. If there is risk that in some cases G1 is worse than CMS, it may
be a better choice to make G1 an optional choice first by offering another
conf/cassandra-env-g1.sh file to let people have a try and don't change the
default settings.
For the tests comparing G1 and CMS, does the tests cover some extreme case? For
example: bootstrap/rebuild/remove node, repair, lots of queries over
tombstone_failure_threshold... And I think each test should take at lease 24
hours to have several full GCs to estimate the latency.
Furthermore, now using CMS, we have a max heap size (8GB) limit even if the
memory of this node is very large. If we decide to change the default gc
algorithm, what is the suitable new limit?
> 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: 2.1.6
>
>
> 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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