On Fri, 16 May 2025 12:18:42 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
> This change uses a ConcurrentHashTable to associate Method* with jmethodID, > instead of an indirection. JNI is deprecated in favor of using Panama to > call methods, so I don't think we're concerned about performance going > forward. JVMTI uses a lot of jmethodIDs but there aren't any performance > tests for JVMTI, but running vmTestbase/nsk/jvmti with in product build with > and without this change had no difference in time. > > The purpose of this change is to remove the memory leak when you unload > classes: we were leaving the jmethodID memory just in case JVMTI code still > had references to that jmethodID and instead of crashing, should get nullptr. > With this change, if JVMTI looks up a jmethodID, we've removed it from the > table and will return nullptr. Redefinition and the > InstanceKlass::_jmethod_method_ids is somewhat complicated. When a method > becomes "obsolete" in redefinition, which means that the code in the method > is changed, afterward creating a jmethodID from an "obsolete" method will > create a new entry in the InstanceKlass table. This mechanism increases the > method_idnum to do this. In the future maybe we could throw > NoSuchMethodError if you try to create a jmethodID out of an obsolete method > and remove all this code. But that's not in this change. > > Tested with tier1-4, 5-7. Also, this was @fisk 's idea. ------------- PR Comment: https://git.openjdk.org/jdk/pull/25267#issuecomment-2967389860
