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 an approximation of the number of > versions found for the entry being looked up, which will 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. This pull request has now been integrated. Changeset: d49f2104 Author: Eirik Bjørsnøs <eir...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/d49f21043b84ebcc8b9176de3a84621ca7bca8fb Stats: 99 lines in 4 files changed: 36 ins; 35 del; 28 mod 8342040: Further improve entry lookup performance for multi-release JARs Co-authored-by: Claes Redestad <redes...@openjdk.org> Reviewed-by: redestad ------------- PR: https://git.openjdk.org/jdk/pull/21489
