jdk-sandbox: comparison hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp

equal deleted inserted replaced

-:6751eb6eceb0
+:60de0264afe8
 double start_vtime_sec = os::elapsedVTime();
 double start_time_sec = os::elapsedTime();
 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
 the_task->do_marking_step(mark_step_duration_ms,
-true /* do_stealing    */,
+true  /* do_termination */,
-true /* do_termination */);
+false /* is_serial*/);
 double end_time_sec = os::elapsedTime();
 double end_vtime_sec = os::elapsedVTime();
 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
 double elapsed_time_sec = end_time_sec - start_time_sec;
 // state. Also using the tasks' local queues removes the potential
 // of the workers interfering with each other that could occur if
 // operating on the global stack.
 class G1CMKeepAliveAndDrainClosure: public OopClosure {
-ConcurrentMark*  _cm;
+ConcurrentMark* _cm;
-CMTask*          _task;
+CMTask*         _task;
-int              _ref_counter_limit;
+int             _ref_counter_limit;
-int              _ref_counter;
+int             _ref_counter;
+bool            _is_serial;
 public:
-G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task) :
+G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
-_cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval) {
+_cm(cm), _task(task), _is_serial(is_serial),
+_ref_counter_limit(G1RefProcDrainInterval) {
 assert(_ref_counter_limit > 0, "sanity");
+assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
 _ref_counter = _ref_counter_limit;
 }
 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
 virtual void do_oop(      oop* p) { do_oop_work(p); }
 // when CMTask::do_marking_step() returns without setting the
 // has_aborted() flag that the marking step has completed.
 do {
 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
 _task->do_marking_step(mark_step_duration_ms,
-false /* do_stealing    */,
+false      /* do_termination */,
-false /* do_termination */);
+_is_serial);
 } while (_task->has_aborted() && !_cm->has_overflown());
 _ref_counter = _ref_counter_limit;
 }
 } else {
 if (_cm->verbose_high()) {
 // added by the 'keep alive' oop closure above.
 class G1CMDrainMarkingStackClosure: public VoidClosure {
 ConcurrentMark* _cm;
 CMTask*         _task;
-bool            _do_stealing;
+bool            _is_serial;
-bool            _do_termination;
 public:
-G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_par) :
+G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
-_cm(cm), _task(task) {
+_cm(cm), _task(task), _is_serial(is_serial) {
-assert(is_par || _task->worker_id() == 0,
+assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
-"Only task for worker 0 should be used if ref processing is single threaded");
-// We only allow stealing and only enter the termination protocol
-// in CMTask::do_marking_step() if this closure is being instantiated
-// for parallel reference processing.
-_do_stealing = _do_termination = is_par;
 }
 void do_void() {
 do {
 if (_cm->verbose_high()) {
-gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - "
+gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s",
-"stealing: %s, termination: %s",
+_task->worker_id(), BOOL_TO_STR(_is_serial));
-_task->worker_id(),
-BOOL_TO_STR(_do_stealing),
-BOOL_TO_STR(_do_termination));
 }
 // We call CMTask::do_marking_step() to completely drain the local
 // and global marking stacks of entries pushed by the 'keep alive'
 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
 // one of which is reaching the specified time target.) It is only
 // when CMTask::do_marking_step() returns without setting the
 // has_aborted() flag that the marking step has completed.
 _task->do_marking_step(1000000000.0 /* something very large */,
-_do_stealing,
+true         /* do_termination */,
-_do_termination);
+_is_serial);
 } while (_task->has_aborted() && !_cm->has_overflown());
 }
 };
 // Implementation of AbstractRefProcTaskExecutor for parallel
 class G1CMRefProcTaskProxy: public AbstractGangTask {
 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 ProcessTask&     _proc_task;
 G1CollectedHeap* _g1h;
 ConcurrentMark*  _cm;
-bool             _processing_is_mt;
 public:
 G1CMRefProcTaskProxy(ProcessTask& proc_task,
 G1CollectedHeap* g1h,
 ConcurrentMark* cm) :
 AbstractGangTask("Process reference objects in parallel"),
 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
 ReferenceProcessor* rp = _g1h->ref_processor_cm();
-_processing_is_mt = rp->processing_is_mt();
+assert(rp->processing_is_mt(), "shouldn't be here otherwise");
 }
 virtual void work(uint worker_id) {
-CMTask* marking_task = _cm->task(worker_id);
+CMTask* task = _cm->task(worker_id);
 G1CMIsAliveClosure g1_is_alive(_g1h);
-G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, marking_task);
+G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
-G1CMDrainMarkingStackClosure g1_par_drain(_cm, marking_task, _processing_is_mt);
+G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
 }
 };
 // Set the soft reference policy
 rp->setup_policy(clear_all_soft_refs);
 assert(_markStack.isEmpty(), "mark stack should be empty");
-// Non-MT instances 'Keep Alive' and 'Complete GC' oop closures.
+// Instances of the 'Keep Alive' and 'Complete GC' closures used
-G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0));
+// in serial reference processing. Note these closures are also
-G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), false);
+// used for serially processing (by the the current thread) the
+// JNI references during parallel reference processing.
-// We need at least one active thread. If reference processing is
+//
-// not multi-threaded we use the current (ConcurrentMarkThread) thread,
+// These closures do not need to synchronize with the worker
-// otherwise we use the work gang from the G1CollectedHeap and we
+// threads involved in parallel reference processing as these
-// utilize all the worker threads we can.
+// instances are executed serially by the current thread (e.g.
-uint active_workers = (rp->processing_is_mt() && g1h->workers() != NULL
+// reference processing is not multi-threaded and is thus
-? g1h->workers()->active_workers()
+// performed by the current thread instead of a gang worker).
-: 1U);
+//
+// The gang tasks involved in parallel reference procssing create
+// their own instances of these closures, which do their own
+// synchronization among themselves.
+G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
+G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
+// We need at least one active thread. If reference processing
+// is not multi-threaded we use the current (VMThread) thread,
+// otherwise we use the work gang from the G1CollectedHeap and
+// we utilize all the worker threads we can.
+bool processing_is_mt = rp->processing_is_mt() && g1h->workers() != NULL;
+uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
+// Parallel processing task executor.
 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
 g1h->workers(), active_workers);
+AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
-AbstractRefProcTaskExecutor* executor = (rp->processing_is_mt()
-? &par_task_executor
-: NULL);
 // Set the degree of MT processing here.  If the discovery was done MT,
 // the number of threads involved during discovery could differ from
 // the number of active workers.  This is OK as long as the discovered
 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
 // oop closures will set the has_overflown flag if we overflow the
 // global marking stack.
 assert(_markStack.overflow() || _markStack.isEmpty(),
 "mark stack should be empty (unless it overflowed)");
 if (_markStack.overflow()) {
 // This should have been done already when we tried to push an
 // entry on to the global mark stack. But let's do it again.
 set_has_overflown();
 }
 _nextMarkBitMap  = (CMBitMap*)  temp;
 }
 class CMRemarkTask: public AbstractGangTask {
 private:
-ConcurrentMark *_cm;
+ConcurrentMark* _cm;
+bool            _is_serial;
 public:
 void work(uint worker_id) {
 // Since all available tasks are actually started, we should
 // only proceed if we're supposed to be actived.
 if (worker_id < _cm->active_tasks()) {
 CMTask* task = _cm->task(worker_id);
 task->record_start_time();
 do {
 task->do_marking_step(1000000000.0 /* something very large */,
-true /* do_stealing    */,
+true         /* do_termination       */,
-true /* do_termination */);
+_is_serial);
 } while (task->has_aborted() && !_cm->has_overflown());
 // If we overflow, then we do not want to restart. We instead
 // want to abort remark and do concurrent marking again.
 task->record_end_time();
 }
 }
-CMRemarkTask(ConcurrentMark* cm, int active_workers) :
+CMRemarkTask(ConcurrentMark* cm, int active_workers, bool is_serial) :
-AbstractGangTask("Par Remark"), _cm(cm) {
+AbstractGangTask("Par Remark"), _cm(cm), _is_serial(is_serial) {
 _cm->terminator()->reset_for_reuse(active_workers);
 }
 };
 void ConcurrentMark::checkpointRootsFinalWork() {
 // Leave _parallel_marking_threads at it's
 // value originally calculated in the ConcurrentMark
 // constructor and pass values of the active workers
 // through the gang in the task.
-CMRemarkTask remarkTask(this, active_workers);
+CMRemarkTask remarkTask(this, active_workers, false /* is_serial */);
+// We will start all available threads, even if we decide that the
+// active_workers will be fewer. The extra ones will just bail out
+// immediately.
 g1h->set_par_threads(active_workers);
 g1h->workers()->run_task(&remarkTask);
 g1h->set_par_threads(0);
 } else {
 G1CollectedHeap::StrongRootsScope srs(g1h);
-// this is remark, so we'll use up all available threads
 uint active_workers = 1;
 set_phase(active_workers, false /* concurrent */);
-CMRemarkTask remarkTask(this, active_workers);
+// Note - if there's no work gang then the VMThread will be
-// We will start all available threads, even if we decide that the
+// the thread to execute the remark - serially. We have
-// active_workers will be fewer. The extra ones will just bail out
+// to pass true for the is_serial parameter so that
-// immediately.
+// CMTask::do_marking_step() doesn't enter the sync
+// barriers in the event of an overflow. Doing so will
+// cause an assert that the current thread is not a
+// concurrent GC thread.
+CMRemarkTask remarkTask(this, active_workers, true /* is_serial*/);
 remarkTask.work(0);
 }
 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
 guarantee(satb_mq_set.completed_buffers_num() == 0, "invariant");
 #endif // _MARKING_STATS_
 }
 /*****************************************************************************
-The do_marking_step(time_target_ms) method is the building block
+The do_marking_step(time_target_ms, ...) method is the building
-of the parallel marking framework. It can be called in parallel
+block of the parallel marking framework. It can be called in parallel
 with other invocations of do_marking_step() on different tasks
 (but only one per task, obviously) and concurrently with the
 mutator threads, or during remark, hence it eliminates the need
 for two versions of the code. When called during remark, it will
 pick up from where the task left off during the concurrent marking
 phase. Interestingly, tasks are also claimable during evacuation
 pauses too, since do_marking_step() ensures that it aborts before
 it needs to yield.
-The data structures that is uses to do marking work are the
+The data structures that it uses to do marking work are the
 following:
 (1) Marking Bitmap. If there are gray objects that appear only
 on the bitmap (this happens either when dealing with an overflow
 or when the initial marking phase has simply marked the roots
 too. The initial reason for the clock method was to avoid calling
 vtime too regularly, as it is quite expensive. So, once it was in
 place, it was natural to piggy-back all the other conditions on it
 too and not constantly check them throughout the code.
+If do_termination is true then do_marking_step will enter its
+termination protocol.
+The value of is_serial must be true when do_marking_step is being
+called serially (i.e. by the VMThread) and do_marking_step should
+skip any synchronization in the termination and overflow code.
+Examples include the serial remark code and the serial reference
+processing closures.
+The value of is_serial must be false when do_marking_step is
+being called by any of the worker threads in a work gang.
+Examples include the concurrent marking code (CMMarkingTask),
+the MT remark code, and the MT reference processing closures.
 *****************************************************************************/
 void CMTask::do_marking_step(double time_target_ms,
-bool do_stealing,
+bool do_termination,
-bool do_termination) {
+bool is_serial) {
 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
 assert(concurrent() == _cm->concurrent(), "they should be the same");
 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
 assert(_task_queues != NULL, "invariant");
 // catch most problems.
 _claimed = true;
 _start_time_ms = os::elapsedVTime() * 1000.0;
 statsOnly( _interval_start_time_ms = _start_time_ms );
+// If do_stealing is true then do_marking_step will attempt to
+// steal work from the other CMTasks. It only makes sense to
+// enable stealing when the termination protocol is enabled
+// and do_marking_step() is not being called serially.
+bool do_stealing = do_termination && !is_serial;
 double diff_prediction_ms =
 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
 _time_target_ms = time_target_ms - diff_prediction_ms;
 if (_cm->verbose_low()) {
 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
 }
 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
 // The CMTask class also extends the TerminatorTerminator class,
 // hence its should_exit_termination() method will also decide
 // whether to exit the termination protocol or not.
-bool finished = _cm->terminator()->offer_termination(this);
+bool finished = (is_serial ||
+_cm->terminator()->offer_termination(this));
 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
 _termination_time_ms +=
 termination_end_time_ms - _termination_start_time_ms;
 if (finished) {
 if (_cm->verbose_low()) {
 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
 }
-_cm->enter_first_sync_barrier(_worker_id);
+if (!is_serial) {
-// When we exit this sync barrier we know that all tasks have
+// We only need to enter the sync barrier if being called
-// stopped doing marking work. So, it's now safe to
+// from a parallel context
-// re-initialise our data structures. At the end of this method,
+_cm->enter_first_sync_barrier(_worker_id);
-// task 0 will clear the global data structures.
+// When we exit this sync barrier we know that all tasks have
+// stopped doing marking work. So, it's now safe to
+// re-initialise our data structures. At the end of this method,
+// task 0 will clear the global data structures.
+}
 statsOnly( ++_aborted_overflow );
 // We clear the local state of this task...
 clear_region_fields();
-// ...and enter the second barrier.
+if (!is_serial) {
-_cm->enter_second_sync_barrier(_worker_id);
+// ...and enter the second barrier.
+_cm->enter_second_sync_barrier(_worker_id);
+}
 // At this point everything has bee re-initialised and we're
 // ready to restart.
 }
 if (_cm->verbose_low()) {

changeset 16388	60de0264afe8
parent 15960	674d0586183f
child 16389	70f98431dd29