I'm surprised we released 4.0 without changing the default to G1 given that many Cassandra deployments have changed the project's default because it is incorrect. I know that 7486 broke a user 7 years ago, but I think we have had a ton of testing since then in the community to build our confidence. Not to mention that Java 9+ (released 2017) made G1 the default and Java 14 (2020) removes CMS entirely.
I have personally done targeted AB testing of G1GC vs CMS in a controlled fashion using NDBench and our team had enough confidence in ~2019 to roll it to Netflix's entire fleet of O(1k) clusters and O(10k) instances running Java 8. We found it vastly superior to CMS in practically every way (no more 10s+ compacting STW phases after heap fragmentation, better tail latency at a coordinator/replica level, better average throughput, etc ...), and only identified a single very minor p99 regression on one cluster (~5%) which we didn't consider severe enough to roll back. Right now our project defaults are hurting 99 users to help 1; let that one user change the defaults? 4.1 seems like a great place to fix the bug, absent being able to do that let's at least fix it in trunk? -Joey On Thu, Nov 17, 2022 at 8:27 AM Jon Haddad <rustyrazorbl...@apache.org> wrote: > > I noticed nobody answered my actual question - what would it take for you to > be comfortable? > > It seems that the need to do a release is now more important than the best > interests of the new user's experience - despite having plenty of > *production* experience showing that what we ship isn't even remotely close > to usable. > > I tried to offer a compromise, and it's not cool with me that it was ignored > by everyone objecting. > > Jon > > On 2022/11/17 08:34:53 Mick Semb Wever wrote: > > Ok, wrt G1 default, this is won't go ahead for 4.1-rc1 > > > > We can revisit it for 4.1.x > > > > We have a lot of voices here adamantly positive for it, and those of us > > that have done the performance testing over the years know why. But being > > called to prove it is totally valid, if you have data to any such tests > > please add them to the ticket 18027 > >
