From 3842bd39e10612c7eef36c6048407e81bcd0a8fb Mon Sep 17 00:00:00 2001 From: buchgr Date: Mon, 23 Jul 2018 05:43:41 -0700 Subject: jdk: use parallel old gc and disable compact strings When switching to JDK9 we regressed on java build performance by about ~30%. We found that when using parallel gc instead of G1 and disabling compact strings for JavaBuilder, the java build performance is "only" 10% slower. We additionally found JDK9 to have a significantly higher startup time. This impacts the performance of tools like javac and tubine and we believe that this accounts for most of the remaining overhead that can't be explained by disabling G1 and compact strings. java8 -version: 80ms java9 -version: 140ms java10 -version: 110ms Additionally, we found that the number of modules shipped with the JDK have a direct effect on the startup time. When building Java 10 with only the 9 modules required by Bazel we find that the startup time reduces to 80ms (from 110ms) which is on par with Java 8. We thus expect the regression to be fixed by a future migration to Java 10, which should be done in one of the next Bazel releases. == Some benchmark results == https://github.com/google/protobuf $ bazel build :protobuf_java Bazel 0.15.2: 4.2s Bazel 0.16.0-rc2: 5.2s This Change: 4.2s https://github.com/jin/android-projects/tree/master/java_only $ bazel build :module0 Bazel 0.15.2: 8.2s Bazel 0.16.0-rc2: 11.5s This Change: 9.1s RELNOTES: None PiperOrigin-RevId: 205647957 --- tools/jdk/default_java_toolchain.bzl | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'tools') diff --git a/tools/jdk/default_java_toolchain.bzl b/tools/jdk/default_java_toolchain.bzl index f4dc03577c..c518d026b3 100644 --- a/tools/jdk/default_java_toolchain.bzl +++ b/tools/jdk/default_java_toolchain.bzl @@ -19,6 +19,10 @@ JDK8_JVM_OPTS = [ ] JDK9_JVM_OPTS = [ + # In JDK9 we have seen a ~30% slow down in JavaBuilder performance when using + # G1 collector and having compact strings enabled. + "-XX:+UseParallelOldGC", + "-XX:-CompactStrings", # Allow JavaBuilder to access internal javac APIs. "--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED", "--add-exports=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED", -- cgit v1.2.3