Shard srcjars when sharding javac compilation
java_library rules with javac_shard_size set split the sources into
shards to invoke javac multiple times, but were using a single javac
invocation for all srcjars. For fraemwork-minus-apex, this srcjar
shard was the long pole at 15.7 seconds, containing 266 srcjars with
1542 java files with a total of 614593 lines.
Use a rough approximation of 5 sources per srcjar to determine the
number of shards to split the srcjars into based on javac_shard_size.
This results in splitting the srcjars for frameworks-minus-apex into
8 shards, with the longest taking 10.5 seconds to compile.
The longest shard contains most of the aidl srcjars, which have been
generated by sharded groups of 50 aidl files and have a much higher
average number of sources per srcjar (a mean and median of 27). A
future improvement could be to shard those separately assuming a
higher number of sources per srcjar.
Bug: 302033097
Test: USE_RBE=false m frameworks-minus-apex
Change-Id: I85e740c7fcf5651cf18c0cdc90ab8c6ee39cb47b
diff --git a/java/base.go b/java/base.go
index 2c0b3ea..653323a 100644
--- a/java/base.go
+++ b/java/base.go
@@ -1343,10 +1343,17 @@
jars = append(jars, classes)
}
}
+ // Assume approximately 5 sources per srcjar.
+ // For framework-minus-apex in AOSP at the time this was written, there are 266 srcjars, with a mean
+ // of 5.8 sources per srcjar, but a median of 1, a standard deviation of 10, and a max of 48 source files.
if len(srcJars) > 0 {
- classes := j.compileJavaClasses(ctx, jarName, len(shardSrcs),
- nil, srcJars, flags, extraJarDeps)
- jars = append(jars, classes)
+ startIdx := len(shardSrcs)
+ shardSrcJarsList := android.ShardPaths(srcJars, shardSize/5)
+ for idx, shardSrcJars := range shardSrcJarsList {
+ classes := j.compileJavaClasses(ctx, jarName, startIdx+idx,
+ nil, shardSrcJars, flags, extraJarDeps)
+ jars = append(jars, classes)
+ }
}
} else {
classes := j.compileJavaClasses(ctx, jarName, -1, uniqueJavaFiles, srcJars, flags, extraJarDeps)