Method timerLoop

src/j9StackTraces.cpp:79–150

}

void J9StackTraces::timerLoop() {
    JNIEnv* jni = VM::attachThread("Async-profiler Sampler");
    storeRelease(_self_env, jni);

    jni->PushLocalFrame(64);

    jvmtiEnv* jvmti = VM::jvmti();
    char notification_buf[65536];
    std::map<void*, jthread> known_threads;

    int max_frames = _max_stack_depth + MAX_J9_NATIVE_FRAMES + RESERVED_FRAMES;
    ASGCT_CallFrame* frames = (ASGCT_CallFrame*)malloc(max_frames * sizeof(ASGCT_CallFrame));
    jvmtiFrameInfoExtended* jvmti_frames = (jvmtiFrameInfoExtended*)malloc(max_frames * sizeof(jvmtiFrameInfoExtended));

    while (true) {
        ssize_t bytes = read(_pipe[0], notification_buf, sizeof(notification_buf));
        if (bytes <= 0) {
            if (bytes < 0 && errno == EAGAIN) {
                continue;
            }
            break;
        }

        ssize_t ptr = 0;
        while (ptr < bytes) {
            J9StackTraceNotification* notif = (J9StackTraceNotification*)(notification_buf + ptr);
            u64 start_time = TSC::ticks();

            jthread thread = known_threads[notif->env];
            jint num_jvmti_frames;
            if (thread == NULL || J9Ext::GetStackTraceExtended(thread, 0, _max_stack_depth, jvmti_frames, &num_jvmti_frames) != 0) {
                jni->PopLocalFrame(NULL);
                jni->PushLocalFrame(64);

                jint thread_count;
                jthread* threads;
                if (jvmti->GetAllThreads(&thread_count, &threads) == 0) {
                    known_threads.clear();
                    for (jint i = 0; i < thread_count; i++) {
                        known_threads[J9Ext::GetJ9vmThread(threads[i])] = threads[i];
                    }
                    jvmti->Deallocate((unsigned char*)threads);
                }

                if ((thread = known_threads[notif->env]) == NULL ||
                    J9Ext::GetStackTraceExtended(thread, 0, _max_stack_depth, jvmti_frames, &num_jvmti_frames) != 0) {
                    continue;
                }
            }

            int num_frames = Profiler::instance()->convertNativeTrace(notif->num_frames, notif->addr, frames, EXECUTION_SAMPLE);

            for (int j = 0; j < num_jvmti_frames; j++) {
                frames[num_frames].method_id = jvmti_frames[j].method;
                frames[num_frames].bci = FrameType::encode(jvmti_frames[j].type, jvmti_frames[j].location);
                num_frames++;
            }