On Wed, 27 Nov 2024 01:04:06 GMT, Chen Liang <li...@openjdk.org> wrote:
>> When core reflection was migrated to be implemented by Method Handles, >> somehow, the method handles are not used for native methods, which are >> generally linkable by method handles. This causes significant performance >> regressions when reflecting native methods, even if their overrides may be >> non-native methods. This is evident in `Object.clone` and `Object.hashCode` >> as shown in the original report. >> >> I believe the blanket restriction previously placed on the native methods >> was because of signature polymorphic methods ([JLS >> 15.12.3](https://docs.oracle.com/javase/specs/jls/se23/html/jls-15.html#jls-15.12.3), >> [JVMS >> 2.9.3](https://docs.oracle.com/javase/specs/jvms/se23/html/jvms-2.html#jvms-2.9.3)) >> for MethodHandle and VarHandle; method handles do not link to the backing >> implementation that throws UOE while core reflection is required to do so. >> I have narrowed the restrictions to be specifically against these methods. >> >> Additionally, I cleaned up another check for invalid varargs flag. >> Together, I clarified the scenarios where native method accessors are used - >> all to bypass restrictions of java.lang.invoke. >> >> Testing: tier 1-5 green > > Chen Liang has updated the pull request with a new target base due to a merge > or a rebase. The incremental webrev excludes the unrelated changes brought in > by the merge/rebase. The pull request contains four additional commits since > the last revision: > > - Review comments > - Merge branch 'master' of https://github.com/openjdk/jdk into > fix/reflect-native-slow > - Better comments > - 8343377: Performance regression in reflective invocation of native methods Marked as reviewed by mchung (Reviewer). src/java.base/share/classes/jdk/internal/reflect/MethodHandleAccessorFactory.java line 376: > 374: // bit set, which verifies that the last parameter of the member > must be > 375: // an array type. Such restriction does not exist in core > reflection > 376: // and the JVM. Fall back to use the native implementation > instead. Suggestion: // For members with ACC_VARARGS bit set, MethodHandles produced by lookup // always have variable arity set and hence the last parameter of the member // must be an array type. Such restriction does not exist in core reflection // and the JVM. Fall back to use the native implementation instead. ------------- PR Review: https://git.openjdk.org/jdk/pull/22169#pullrequestreview-2473723428 PR Review Comment: https://git.openjdk.org/jdk/pull/22169#discussion_r1866489642
