On Mon, 29 Aug 2022 08:55:06 GMT, Aleksey Shipilev <sh...@openjdk.org> wrote:
> `jmod`/`jlink` are executed during build time to produce the `jmod` and the > base modules image. On slow hardware (Raspberry Pi -class, for example) > and/or slow VMs (debug, interpreter-only, for example) this takes a while. > Profiling shows the considerable time is spent on hashing modules either for > writing out the ModuleHash attribute or for verifying the hashes are good. > > Those paths can be parallelized to make them quite faster. > > The major contributors to module hashing are `java.base`, `jdk.desktop` and > `jdk.localedata`, so we have a significant opportunity for parallelism here. > > Motivational improvements on `make clean-images images`: > > > # x86_64 Server, release > > # Baseline > real 0m11.895s > user 1m4.526s > sys 0m10.715s > > # Patched > real 0m10.701s ; <--- 1.1x improvement > user 1m5.097s > sys 0m11.260s > > # x86_64 Zero, release > > # Baseline > real 5m20.335s > user 7m7.791s > sys 0m7.258s > > # Patched > real 2m23.551s ; <--- 2.23x improvement > user 7m14.442s > sys 0m7.856s > > > Additional testing: > - [x] Linux x86_64 fastdebug, `java/util/jar` > - [x] Linux x86_64 fastdebug, `tools/jmod` > - [x] Linux x86_64 fastdebug, `tools/jlink` > - [x] Linux x86_64 fastdebug `tier1` This issue will require discussion as it potentially impacts usage at run-time when the resolver runs at startup or when creating module layers. I also wonder if it has an impact on JDK builds where many jobs are running jmod at the same time. It may be that this has to be configured by a system property so that it can be enabled only in the JDK build. Also just to say that Claes removed all the lambda expressions from this code in JDK 9 to help with startup as that will have to checking too. Also if we are changing this code then we should try to keep the style/conventions/line-lengths consistent where possible. ------------- PR: https://git.openjdk.org/jdk/pull/10060
