On Tue, 26 Jul 2022 12:28:41 GMT, Aleksey Shipilev <sh...@openjdk.org> wrote:
> See the bug for symptoms and rationale. > > In short, after [JDK-8288396](https://bugs.openjdk.org/browse/JDK-8288396) > moved the timestamp to `CFLAGS_VM_VERSION` macro, which changes with every > build, we get Hotspot recompilation every time, even when Hotspot is not > modified. > > I believe current behavior is correct for `--with-source-date=updated` > (current default): you do Hotspot build, you get updated build timestamp, > which forces recompilation of affected compilation units, relinkage, > re-creation of jmods/jimage. The way out is to switch to > `--with-source-date=current`, which would only get the build timestamp at > configure time. > > CIs and build farms are likely reconfiguring before every build anyway, so > their behavior is unlikely to be affected. But this switch definitely > improves the day-to-day OpenJDK development work: it saves >50 seconds on > every `make` for my machine, see below. > > Back-to-back unmodified build before: > > > $ CONF=linux-x86_64-server-release time make hotspot > Building target 'hotspot' in configuration 'linux-x86_64-server-release' > Finished building target 'hotspot' in configuration > 'linux-x86_64-server-release' > > 39.03user 10.97system 0:56.89elapsed 87%CPU (0avgtext+0avgdata > 2048944maxresident)k > 363616inputs+4108072outputs (484major+1100154minor)pagefaults 0swaps > > $ CONF=linux-x86_64-server-release time make hotspot > Building target 'hotspot' in configuration 'linux-x86_64-server-release' > Finished building target 'hotspot' in configuration > 'linux-x86_64-server-release' > > 38.18user 9.02system 0:49.18elapsed 95%CPU (0avgtext+0avgdata > 2048788maxresident)k > 40inputs+4101112outputs (0major+1100077minor)pagefaults 0swaps > > > Back-to-back unmodified build after: > > > $ CONF=linux-x86_64-server-release time make hotspot > Building target 'hotspot' in configuration 'linux-x86_64-server-release' > Finished building target 'hotspot' in configuration > 'linux-x86_64-server-release' > > 2.15user 0.22system 0:02.59elapsed 91%CPU (0avgtext+0avgdata > 49480maxresident)k > 0inputs+176outputs (0major+55506minor)pagefaults 0swaps > > $ CONF=linux-x86_64-server-release time make hotspot > Building target 'hotspot' in configuration 'linux-x86_64-server-release' > Finished building target 'hotspot' in configuration > 'linux-x86_64-server-release' > > 2.18user 0.14system 0:02.46elapsed 94%CPU (0avgtext+0avgdata > 49332maxresident)k Any other opinions? ------------- PR: https://git.openjdk.org/jdk/pull/9638
