>From a user PoV, I'd call G1 drastically friendlier than CMS in that it tends to be well-behaved under a variety of workloads and heap sizes right out of the box without the kind of dark-art tuning and overnight surprises you get with CMS. Granted the smallest heap I have now is 2GB, but that's not really small by 2022 standards and it seems to be the minimum recommended in the docs (though the config calculator will go as low as 1GB)
It feels like the sort of change that wouldn't be a bad surprise in an RC, but maybe a bit too big of a change for backporting to 4.0. On Wed, Nov 9, 2022 at 4:30 PM Josh McKenzie <jmcken...@apache.org> wrote: > fwiw, the "CMS is friendlier for small heaps with C*" conclusion may no > longer be accurate; a lot of work has gone into G1 since the last time > we've covered the topic as a project. Nevermind the changes in C*. > > Lots of moving targets. > > On Wed, Nov 9, 2022, at 6:13 PM, Brad wrote: > > The default garbage collector in Java 11 is G1*. *It's designed to be > self-tuning, so I'd call it friendly. We have run Java 8 and 11 on G1 in > production on all of our 1,000+ clusters for several years. > > I'd agree with Jeremiah that it's worth changing in trunk at the very > least and consider backporting. > > On Wed, Nov 9, 2022 at 5:10 PM Brandon Williams <dri...@gmail.com> wrote: > > If CMS is gone, is there a friendlier alternative to G1? > > On Wed, Nov 9, 2022 at 3:53 PM Josh McKenzie <jmcken...@apache.org> wrote: > > > > My recollection (and brief sleuthing now) surfaces: we've gone back and > forth on the G1 vs. CMS debate over the years and I think we settled on "it > all depends on your environment, workload, and you need to tune it anyway. > It might be worth having a 'default' mode that selects one of the two based > on heap size unless otherwise specified". > > > > I certainly wouldn't make changes to any defaults on a release between > beta and rc personally. > > > > On Wed, Nov 9, 2022, at 4:20 PM, Jeff Jirsa wrote: > > > > G1 you can argue for with the changes in the JDK, though it's MUCH less > friendly to small heaps (e.g. probably our default simple user). > > > > Offheap memtables are different though. If someone wants to attest that > offheap_objects get the same level of rigorous testing as the existing > default, that'd be useful, but I'm pretty sure that's not true, and bugs > like https://issues.apache.org/jira/browse/CASSANDRA-12125 (which > remains undiagnosed) reinforce that it's less commonly used and may have > latent undiscovered bugs for default users. > > > > > > > > > > > > On Wed, Nov 9, 2022 at 11:23 AM Mick Semb Wever <m...@apache.org> wrote: > > > > Any objections to making these changes, at the very last minute, for > 4.1-rc1 ? > > This is CASSANDRA-12029 and CASSANDRA-7486 > > > > Provided we figure out patches for them in the next day or two. > > > > > > > -- This email, including its contents and any attachment(s), may contain confidential and/or proprietary information and is solely for the review and use of the intended recipient(s). If you have received this email in error, please notify the sender and permanently delete this email, its content, and any attachment(s). Any disclosure, copying, or taking of any action in reliance on an email received in error is strictly prohibited.
