On Fri, 5 May 2023 06:45:10 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> Please review this addition to com.sun.management.ThreadMXBean that returns >> the total number of bytes allocated on the Java heap since JVM launch by >> both terminated and live threads. >> >> Because this PR adds a new interface method, I've updated the JMM_VERSION to >> 4, but would be happy to update it to 3_1 instead. > > src/hotspot/share/services/management.cpp line 2102: > >> 2100: JVM_ENTRY(jlong, jmm_GetAllThreadAllocatedMemory(JNIEnv *env)) >> 2101: // There is a race between threads that exit during the loop and >> calling >> 2102: // exited_allocated_bytes. If the result is initialized with >> exited_allocated_bytes, > > If you want a stable and accurate value did you consider holding the > Threads_lock while you iterate the threads? Or do it as a safepoint VMop? The API specification clearly states that this method returns "*an approximation of the total amount of memory allocated in heap*" so in my opinion it is OK to keep it simple here and don't start messing with looks and safepoints. But can't we make this a little more accurate by only adding a threads allocated bytes if it is not `thread->is_terminated()`? Wouldn't that prevent double counting most of the time? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/13814#discussion_r1186246289
