> 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.
Eirik Bjørsnøs has updated the pull request incrementally with four additional commits since the last revision: - Map versions by entry name hashcode instead of by entry name. This avoids String allocation and storage - Merge pull request #1 from cl4es/bitset_versions Use BitSet to streamline construction - Fix traversal, traverse backwards to pick latest applicable version - Use BitSet to streamline construction ------------- Changes: - all: https://git.openjdk.org/jdk/pull/21489/files - new: https://git.openjdk.org/jdk/pull/21489/files/826d78a7..771488e3 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=21489&range=02 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21489&range=01-02 Stats: 65 lines in 3 files changed: 13 ins; 28 del; 24 mod Patch: https://git.openjdk.org/jdk/pull/21489.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/21489/head:pull/21489 PR: https://git.openjdk.org/jdk/pull/21489
