On Tue, 1 Apr 2025 11:59:07 GMT, Magnus Ihse Bursie <i...@openjdk.org> wrote:
> It would be interesting to also see how compilation times varies with > optimization level. At least some kind of hint if HIGHEST is like 2x slower > than LOW, or if SIZE is slower than LOW at all, etc. The relative speed > difference is interesting, but so is it in absolute terms. If a library takes > 0.5 seconds on LOW but 1.1 seconds on HIGH on a particular system, it is > unlikely to matter much to overall build time anywhere. But if it goes from > 15s to 30s on a fast machine, it might be a problem if such performance > regressions stack up, especially on slower machines (which includes the ones > running GHA). This is what I got from my Linux x86_64 system using gcc 13.2.0 devkit (opt build). Note that the build operates on a relatively slow filer, this will slow the build time somewhat but that is true for all opt-levels. rm -rf ./support/modules_libs/jdk.jdwp.agent/libjdwp.so ./jdk/lib/libjdwp.so ./support/native/jdk.jdwp.agent/libjdwp time make jdk.jdwp.agent-libs-only JOBS=1 gave me these times **default (LOW)** real 0m15.661s user 0m8.763s sys 0m2.012s **HIGHEST** real 0m15.201s user 0m9.005s sys 0m2.003s **SIZE** real 0m14.263s user 0m7.905s sys 0m1.891s So it looks like SIZE is a little faster than the other, and LOW and HIGHEST are rather similar. LOW is `-O2` on Linuxx86_64 and HIGHEST is `-O3` , those are maybe rather similar (LOW is a bit misleading because `-O2` is not really that 'low' the gcc docu says about it : 'Optimize even more. GCC performs nearly all supported optimizations that do not involve a space-speed tradeoff.'). ------------- PR Comment: https://git.openjdk.org/jdk/pull/23563#issuecomment-2786694168
