| /* |
| * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "gc/shared/gcId.hpp" |
| #include "gc/shared/workgroup.hpp" |
| #include "memory/allocation.hpp" |
| #include "memory/allocation.inline.hpp" |
| #include "runtime/atomic.inline.hpp" |
| #include "runtime/os.hpp" |
| #include "runtime/semaphore.hpp" |
| #include "runtime/thread.inline.hpp" |
| |
| // Definitions of WorkGang methods. |
| |
| // The current implementation will exit if the allocation |
| // of any worker fails. Still, return a boolean so that |
| // a future implementation can possibly do a partial |
| // initialization of the workers and report such to the |
| // caller. |
| bool AbstractWorkGang::initialize_workers() { |
| |
| if (TraceWorkGang) { |
| tty->print_cr("Constructing work gang %s with %d threads", |
| name(), |
| total_workers()); |
| } |
| _workers = NEW_C_HEAP_ARRAY(AbstractGangWorker*, total_workers(), mtInternal); |
| if (_workers == NULL) { |
| vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create GangWorker array."); |
| return false; |
| } |
| os::ThreadType worker_type; |
| if (are_ConcurrentGC_threads()) { |
| worker_type = os::cgc_thread; |
| } else { |
| worker_type = os::pgc_thread; |
| } |
| for (uint worker = 0; worker < total_workers(); worker += 1) { |
| AbstractGangWorker* new_worker = allocate_worker(worker); |
| assert(new_worker != NULL, "Failed to allocate GangWorker"); |
| _workers[worker] = new_worker; |
| if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) { |
| vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, |
| "Cannot create worker GC thread. Out of system resources."); |
| return false; |
| } |
| if (!DisableStartThread) { |
| os::start_thread(new_worker); |
| } |
| } |
| return true; |
| } |
| |
| AbstractGangWorker* AbstractWorkGang::worker(uint i) const { |
| // Array index bounds checking. |
| AbstractGangWorker* result = NULL; |
| assert(_workers != NULL, "No workers for indexing"); |
| assert(i < total_workers(), "Worker index out of bounds"); |
| result = _workers[i]; |
| assert(result != NULL, "Indexing to null worker"); |
| return result; |
| } |
| |
| void AbstractWorkGang::print_worker_threads_on(outputStream* st) const { |
| uint workers = total_workers(); |
| for (uint i = 0; i < workers; i++) { |
| worker(i)->print_on(st); |
| st->cr(); |
| } |
| } |
| |
| void AbstractWorkGang::threads_do(ThreadClosure* tc) const { |
| assert(tc != NULL, "Null ThreadClosure"); |
| uint workers = total_workers(); |
| for (uint i = 0; i < workers; i++) { |
| tc->do_thread(worker(i)); |
| } |
| } |
| |
| // WorkGang dispatcher implemented with semaphores. |
| // |
| // Semaphores don't require the worker threads to re-claim the lock when they wake up. |
| // This helps lowering the latency when starting and stopping the worker threads. |
| class SemaphoreGangTaskDispatcher : public GangTaskDispatcher { |
| // The task currently being dispatched to the GangWorkers. |
| AbstractGangTask* _task; |
| |
| volatile uint _started; |
| volatile uint _not_finished; |
| |
| // Semaphore used to start the GangWorkers. |
| Semaphore* _start_semaphore; |
| // Semaphore used to notify the coordinator that all workers are done. |
| Semaphore* _end_semaphore; |
| |
| public: |
| SemaphoreGangTaskDispatcher() : |
| _task(NULL), |
| _started(0), |
| _not_finished(0), |
| _start_semaphore(new Semaphore()), |
| _end_semaphore(new Semaphore()) |
| { } |
| |
| ~SemaphoreGangTaskDispatcher() { |
| delete _start_semaphore; |
| delete _end_semaphore; |
| } |
| |
| void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) { |
| // No workers are allowed to read the state variables until they have been signaled. |
| _task = task; |
| _not_finished = num_workers; |
| |
| // Dispatch 'num_workers' number of tasks. |
| _start_semaphore->signal(num_workers); |
| |
| // Wait for the last worker to signal the coordinator. |
| _end_semaphore->wait(); |
| |
| // No workers are allowed to read the state variables after the coordinator has been signaled. |
| assert(_not_finished == 0, "%d not finished workers?", _not_finished); |
| _task = NULL; |
| _started = 0; |
| |
| } |
| |
| WorkData worker_wait_for_task() { |
| // Wait for the coordinator to dispatch a task. |
| _start_semaphore->wait(); |
| |
| uint num_started = (uint) Atomic::add(1, (volatile jint*)&_started); |
| |
| // Subtract one to get a zero-indexed worker id. |
| uint worker_id = num_started - 1; |
| |
| return WorkData(_task, worker_id); |
| } |
| |
| void worker_done_with_task() { |
| // Mark that the worker is done with the task. |
| // The worker is not allowed to read the state variables after this line. |
| uint not_finished = (uint) Atomic::add(-1, (volatile jint*)&_not_finished); |
| |
| // The last worker signals to the coordinator that all work is completed. |
| if (not_finished == 0) { |
| _end_semaphore->signal(); |
| } |
| } |
| }; |
| |
| class MutexGangTaskDispatcher : public GangTaskDispatcher { |
| AbstractGangTask* _task; |
| |
| volatile uint _started; |
| volatile uint _finished; |
| volatile uint _num_workers; |
| |
| Monitor* _monitor; |
| |
| public: |
| MutexGangTaskDispatcher() |
| : _task(NULL), |
| _monitor(new Monitor(Monitor::leaf, "WorkGang dispatcher lock", false, Monitor::_safepoint_check_never)), |
| _started(0), |
| _finished(0), |
| _num_workers(0) {} |
| |
| ~MutexGangTaskDispatcher() { |
| delete _monitor; |
| } |
| |
| void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) { |
| MutexLockerEx ml(_monitor, Mutex::_no_safepoint_check_flag); |
| |
| _task = task; |
| _num_workers = num_workers; |
| |
| // Tell the workers to get to work. |
| _monitor->notify_all(); |
| |
| // Wait for them to finish. |
| while (_finished < _num_workers) { |
| _monitor->wait(/* no_safepoint_check */ true); |
| } |
| |
| _task = NULL; |
| _num_workers = 0; |
| _started = 0; |
| _finished = 0; |
| } |
| |
| WorkData worker_wait_for_task() { |
| MonitorLockerEx ml(_monitor, Mutex::_no_safepoint_check_flag); |
| |
| while (_num_workers == 0 || _started == _num_workers) { |
| _monitor->wait(/* no_safepoint_check */ true); |
| } |
| |
| _started++; |
| |
| // Subtract one to get a zero-indexed worker id. |
| uint worker_id = _started - 1; |
| |
| return WorkData(_task, worker_id); |
| } |
| |
| void worker_done_with_task() { |
| MonitorLockerEx ml(_monitor, Mutex::_no_safepoint_check_flag); |
| |
| _finished++; |
| |
| if (_finished == _num_workers) { |
| // This will wake up all workers and not only the coordinator. |
| _monitor->notify_all(); |
| } |
| } |
| }; |
| |
| static GangTaskDispatcher* create_dispatcher() { |
| if (UseSemaphoreGCThreadsSynchronization) { |
| return new SemaphoreGangTaskDispatcher(); |
| } |
| |
| return new MutexGangTaskDispatcher(); |
| } |
| |
| WorkGang::WorkGang(const char* name, |
| uint workers, |
| bool are_GC_task_threads, |
| bool are_ConcurrentGC_threads) : |
| AbstractWorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads), |
| _dispatcher(create_dispatcher()) |
| { } |
| |
| AbstractGangWorker* WorkGang::allocate_worker(uint worker_id) { |
| return new GangWorker(this, worker_id); |
| } |
| |
| void WorkGang::run_task(AbstractGangTask* task) { |
| _dispatcher->coordinator_execute_on_workers(task, active_workers()); |
| } |
| |
| AbstractGangWorker::AbstractGangWorker(AbstractWorkGang* gang, uint id) { |
| _gang = gang; |
| set_id(id); |
| set_name("%s#%d", gang->name(), id); |
| } |
| |
| void AbstractGangWorker::run() { |
| initialize(); |
| loop(); |
| } |
| |
| void AbstractGangWorker::initialize() { |
| this->record_stack_base_and_size(); |
| this->initialize_named_thread(); |
| assert(_gang != NULL, "No gang to run in"); |
| os::set_priority(this, NearMaxPriority); |
| if (TraceWorkGang) { |
| tty->print_cr("Running gang worker for gang %s id %u", |
| gang()->name(), id()); |
| } |
| // The VM thread should not execute here because MutexLocker's are used |
| // as (opposed to MutexLockerEx's). |
| assert(!Thread::current()->is_VM_thread(), "VM thread should not be part" |
| " of a work gang"); |
| } |
| |
| bool AbstractGangWorker::is_GC_task_thread() const { |
| return gang()->are_GC_task_threads(); |
| } |
| |
| bool AbstractGangWorker::is_ConcurrentGC_thread() const { |
| return gang()->are_ConcurrentGC_threads(); |
| } |
| |
| void AbstractGangWorker::print_on(outputStream* st) const { |
| st->print("\"%s\" ", name()); |
| Thread::print_on(st); |
| st->cr(); |
| } |
| |
| WorkData GangWorker::wait_for_task() { |
| return gang()->dispatcher()->worker_wait_for_task(); |
| } |
| |
| void GangWorker::signal_task_done() { |
| gang()->dispatcher()->worker_done_with_task(); |
| } |
| |
| void GangWorker::print_task_started(WorkData data) { |
| if (TraceWorkGang) { |
| tty->print_cr("Running work gang %s task %s worker %u", name(), data._task->name(), data._worker_id); |
| } |
| } |
| |
| void GangWorker::print_task_done(WorkData data) { |
| if (TraceWorkGang) { |
| tty->print_cr("\nFinished work gang %s task %s worker %u", name(), data._task->name(), data._worker_id); |
| Thread* me = Thread::current(); |
| tty->print_cr(" T: " PTR_FORMAT " VM_thread: %d", p2i(me), me->is_VM_thread()); |
| } |
| } |
| |
| void GangWorker::run_task(WorkData data) { |
| print_task_started(data); |
| |
| GCIdMark gc_id_mark(data._task->gc_id()); |
| data._task->work(data._worker_id); |
| |
| print_task_done(data); |
| } |
| |
| void GangWorker::loop() { |
| while (true) { |
| WorkData data = wait_for_task(); |
| |
| run_task(data); |
| |
| signal_task_done(); |
| } |
| } |
| |
| // *** WorkGangBarrierSync |
| |
| WorkGangBarrierSync::WorkGangBarrierSync() |
| : _monitor(Mutex::safepoint, "work gang barrier sync", true, |
| Monitor::_safepoint_check_never), |
| _n_workers(0), _n_completed(0), _should_reset(false), _aborted(false) { |
| } |
| |
| WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name) |
| : _monitor(Mutex::safepoint, name, true, Monitor::_safepoint_check_never), |
| _n_workers(n_workers), _n_completed(0), _should_reset(false), _aborted(false) { |
| } |
| |
| void WorkGangBarrierSync::set_n_workers(uint n_workers) { |
| _n_workers = n_workers; |
| _n_completed = 0; |
| _should_reset = false; |
| _aborted = false; |
| } |
| |
| bool WorkGangBarrierSync::enter() { |
| MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag); |
| if (should_reset()) { |
| // The should_reset() was set and we are the first worker to enter |
| // the sync barrier. We will zero the n_completed() count which |
| // effectively resets the barrier. |
| zero_completed(); |
| set_should_reset(false); |
| } |
| inc_completed(); |
| if (n_completed() == n_workers()) { |
| // At this point we would like to reset the barrier to be ready in |
| // case it is used again. However, we cannot set n_completed() to |
| // 0, even after the notify_all(), given that some other workers |
| // might still be waiting for n_completed() to become == |
| // n_workers(). So, if we set n_completed() to 0, those workers |
| // will get stuck (as they will wake up, see that n_completed() != |
| // n_workers() and go back to sleep). Instead, we raise the |
| // should_reset() flag and the barrier will be reset the first |
| // time a worker enters it again. |
| set_should_reset(true); |
| monitor()->notify_all(); |
| } else { |
| while (n_completed() != n_workers() && !aborted()) { |
| monitor()->wait(/* no_safepoint_check */ true); |
| } |
| } |
| return !aborted(); |
| } |
| |
| void WorkGangBarrierSync::abort() { |
| MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag); |
| set_aborted(); |
| monitor()->notify_all(); |
| } |
| |
| // SubTasksDone functions. |
| |
| SubTasksDone::SubTasksDone(uint n) : |
| _n_tasks(n), _tasks(NULL) { |
| _tasks = NEW_C_HEAP_ARRAY(uint, n, mtInternal); |
| guarantee(_tasks != NULL, "alloc failure"); |
| clear(); |
| } |
| |
| bool SubTasksDone::valid() { |
| return _tasks != NULL; |
| } |
| |
| void SubTasksDone::clear() { |
| for (uint i = 0; i < _n_tasks; i++) { |
| _tasks[i] = 0; |
| } |
| _threads_completed = 0; |
| #ifdef ASSERT |
| _claimed = 0; |
| #endif |
| } |
| |
| bool SubTasksDone::is_task_claimed(uint t) { |
| assert(t < _n_tasks, "bad task id."); |
| uint old = _tasks[t]; |
| if (old == 0) { |
| old = Atomic::cmpxchg(1, &_tasks[t], 0); |
| } |
| assert(_tasks[t] == 1, "What else?"); |
| bool res = old != 0; |
| #ifdef ASSERT |
| if (!res) { |
| assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?"); |
| Atomic::inc((volatile jint*) &_claimed); |
| } |
| #endif |
| return res; |
| } |
| |
| void SubTasksDone::all_tasks_completed(uint n_threads) { |
| jint observed = _threads_completed; |
| jint old; |
| do { |
| old = observed; |
| observed = Atomic::cmpxchg(old+1, &_threads_completed, old); |
| } while (observed != old); |
| // If this was the last thread checking in, clear the tasks. |
| uint adjusted_thread_count = (n_threads == 0 ? 1 : n_threads); |
| if (observed + 1 == (jint)adjusted_thread_count) { |
| clear(); |
| } |
| } |
| |
| |
| SubTasksDone::~SubTasksDone() { |
| if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks); |
| } |
| |
| // *** SequentialSubTasksDone |
| |
| void SequentialSubTasksDone::clear() { |
| _n_tasks = _n_claimed = 0; |
| _n_threads = _n_completed = 0; |
| } |
| |
| bool SequentialSubTasksDone::valid() { |
| return _n_threads > 0; |
| } |
| |
| bool SequentialSubTasksDone::is_task_claimed(uint& t) { |
| uint* n_claimed_ptr = &_n_claimed; |
| t = *n_claimed_ptr; |
| while (t < _n_tasks) { |
| jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t); |
| if (res == (jint)t) { |
| return false; |
| } |
| t = *n_claimed_ptr; |
| } |
| return true; |
| } |
| |
| bool SequentialSubTasksDone::all_tasks_completed() { |
| uint* n_completed_ptr = &_n_completed; |
| uint complete = *n_completed_ptr; |
| while (true) { |
| uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete); |
| if (res == complete) { |
| break; |
| } |
| complete = res; |
| } |
| if (complete+1 == _n_threads) { |
| clear(); |
| return true; |
| } |
| return false; |
| } |