On Mon, 13 May 2024 13:03:26 GMT, Evgeny Astigeevich <eastigeev...@openjdk.org> wrote:
> Backout of [JDK-8309271](https://bugs.openjdk.org/browse/JDK-8309271) which > has known bugs, possible bugs and performance issues. REDO work is tracked by > [JDK-8331749](https://bugs.openjdk.org/browse/JDK-8331749). > > Found bugs: > - When refreshing `CompilerDirectivesAddDCmd::execute` will call > `DirectivesStack::hasMatchingDirectives(mh, true)` which only considers the > compiler directive which is on the top of the directives stack. As more than > one directive can be added, `CompilerDirectivesAddDCmd::execute` will not > behave as expected. > - A Java method with old directives might be in the compilation queue. A > request to recompile it with new directives will be ignored. > > There are other concerns: bugs and performance issues. > > Possible bugs: > - `has_matching_directives` might not be cleared. A nmethod might get into > the unloading state before `CodeCache::recompile_marked_directives_matches`. > If the nmethod has been used to mark a Java method and it is the only > nmethod, there will be no nmethod in CodeCache to reach the Java method to > clear the mark. > - A Java method might have been compiled with new directives before > `CodeCache::recompile_marked_directives_matches`. > `CodeCache::recompile_marked_directives_matches` will recompile it again. > - JIT compiler might be compiling a Java method with old directives. A > request to recompile it with new directives will be ignored. > > Performance issues: > - Usually directives are updated for a small number of Java methods. If > CodeCache has thousands of nmethods, > `CodeCache::recompile_marked_directives_matches` will be traversing nmethods > most of which don't need recompilation. > > The backout is not clean because of removal of `CompiledMethod`. > > Tested with release and fastdebug builds: tier1 and tier2 passed. IMO if nobody uses it and the amount of code is small, it is better to back out it and to reimplement it. ------------- PR Comment: https://git.openjdk.org/jdk/pull/19215#issuecomment-2107809381
