On Mon, 14 Oct 2024 11:01:21 GMT, Eirik Bjørsnøs <eir...@openjdk.org> wrote:
> Please review this PR which speeds up `JarFile::getEntry` lookup > significantly for multi-release JAR files. > > The changes in this PR are motivated by the following insights: > > * `META-INF/versions/` is sparsely populated. > * Most entries are not versioned > * The number of unique versions for each versioned entry is small > * Many JAR files are 'accidentally' multi-release; they use the feature to > hide `module-info.class` from Java 8. > > Instead of performing one lookup for every version identified in the JAR, > this PR narrows the version search down to only the number of versions found > for the entry being looked up, which will most often be zero. This speeds up > lookup for non-versioned entries, and provides a more targeted search for > versioned entries. > > An alternative approach could be to normalize the hash code to use the > none-versioned name such that versioned and non-versioned names would be > resolved in the same lookup. This was quickly abandoned since the code > changes were intrusive and mixed too many JAR specific concerns into > `ZipFile`. > > Testing: The existing `JarFileGetEntry` benchmark is updated to optionally > test a multi-release JAR file with one versioned entry for > `module-info.class` plus two other versioned class files for two distinct > versions. Performance results in [first comment](#issuecomment-2410901754). > > Running `ZipFileOpen` on a multi-release JAR did not show a significat > difference between this PR and mainline. > > The JAR and ZIP tests are run locally. GHA results green. The `noreg-perf` > label is added in JBS. Performance results: Baseline: JarFileGetEntry.getEntryHit false 1024 avgt 15 64.619 ? 6.633 ns/op JarFileGetEntry.getEntryHit true 1024 avgt 15 301.770 ? 4.819 ns/op JarFileGetEntry.getEntryHitUncached false 1024 avgt 15 82.030 ? 2.057 ns/op JarFileGetEntry.getEntryHitUncached true 1024 avgt 15 327.966 ? 3.092 ns/op JarFileGetEntry.getEntryMiss false 1024 avgt 15 27.937 ? 0.982 ns/op JarFileGetEntry.getEntryMiss true 1024 avgt 15 267.280 ? 2.196 ns/op JarFileGetEntry.getEntryMissUncached false 1024 avgt 15 53.214 ? 1.085 ns/op JarFileGetEntry.getEntryMissUncached true 1024 avgt 15 290.904 ? 2.359 ns/op PR: Benchmark (mr) (size) Mode Cnt Score Error Units JarFileGetEntry.getEntryHit false 1024 avgt 15 63.311 ? 3.014 ns/op JarFileGetEntry.getEntryHit true 1024 avgt 15 71.333 ? 1.510 ns/op JarFileGetEntry.getEntryHitUncached false 1024 avgt 15 80.401 ? 0.516 ns/op JarFileGetEntry.getEntryHitUncached true 1024 avgt 15 94.810 ? 1.136 ns/op JarFileGetEntry.getEntryMiss false 1024 avgt 15 26.717 ? 0.276 ns/op JarFileGetEntry.getEntryMiss true 1024 avgt 15 45.677 ? 0.412 ns/op JarFileGetEntry.getEntryMissUncached false 1024 avgt 15 53.122 ? 0.954 ns/op JarFileGetEntry.getEntryMissUncached true 1024 avgt 15 66.583 ? 0.425 ns/op ------------- PR Comment: https://git.openjdk.org/jdk/pull/21489#issuecomment-2410901754
