When following up on historical performance for some workloads, we noticed that Renaissance/dotty has regressed slightly after JDK-8301819. Initially found as performance difference between jdk-21+9 and jdk-21+10, we bisected it more accurately to JDK-8301819. The workload requires an extra large warmup to stabilize, which might be why we have not seen in before.

This a small regression compared to the the improvements brought by other major changes in prior releases, but it would be nice to understand and maybe mitigate it further. Might be something as simple as JDK-8300002.

On m7g.16xlarge (Graviton 3):

$ java -Xmx4g -Xms4g -XX:+AlwaysPreTouch -jar renaissance-jmh-0.15.0.jar Dotty -f 20 -wi 200 -i 10
17-ga: 833.063 ± 3.596 ms/op
18-ga: 770.593 ± 2.610 ms/op
19-ga: 726.999 ± 2.711 ms/op
20-ga: 721.737 ± 2.400 ms/op
21+9: 712.865 ± 2.163 ms/op
21+10: 739.913 ± 2.491 ms/op <--- slight regression here
21-ga: 744.847 ± 2.952 ms/op