11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/shared/workgroup.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "runtime/atomic.inline.hpp"
30 #include "runtime/os.hpp"
31
32 // Definitions of WorkGang methods.
33
34 // The current implementation will exit if the allocation
35 // of any worker fails. Still, return a boolean so that
36 // a future implementation can possibly do a partial
37 // initialization of the workers and report such to the
38 // caller.
39 bool AbstractWorkGang::initialize_workers() {
40
41 if (TraceWorkGang) {
42 tty->print_cr("Constructing work gang %s with %d threads",
43 name(),
44 total_workers());
45 }
46 _workers = NEW_C_HEAP_ARRAY(AbstractGangWorker*, total_workers(), mtInternal);
47 if (_workers == NULL) {
48 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create GangWorker array.");
49 return false;
50 }
79 assert(result != NULL, "Indexing to null worker");
80 return result;
81 }
82
83 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
84 uint workers = total_workers();
85 for (uint i = 0; i < workers; i++) {
86 worker(i)->print_on(st);
87 st->cr();
88 }
89 }
90
91 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
92 assert(tc != NULL, "Null ThreadClosure");
93 uint workers = total_workers();
94 for (uint i = 0; i < workers; i++) {
95 tc->do_thread(worker(i));
96 }
97 }
98
99 WorkGang::WorkGang(const char* name,
100 uint workers,
101 bool are_GC_task_threads,
102 bool are_ConcurrentGC_threads) :
103 AbstractWorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads),
104 _started_workers(0),
105 _finished_workers(0),
106 _sequence_number(0),
107 _task(NULL) {
108
109 // Other initialization.
110 _monitor = new Monitor(/* priority */ Mutex::leaf,
111 /* name */ "WorkGroup monitor",
112 /* allow_vm_block */ are_GC_task_threads,
113 Monitor::_safepoint_check_sometimes);
114
115 assert(monitor() != NULL, "Failed to allocate monitor");
116 }
117
118 AbstractGangWorker* WorkGang::allocate_worker(uint worker_id) {
119 return new GangWorker(this, worker_id);
120 }
121
122 void WorkGang::run_task(AbstractGangTask* task) {
123 run_task(task, (uint)active_workers());
124 }
125
126 void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {
127 // This thread is executed by the VM thread which does not block
128 // on ordinary MutexLocker's.
129 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
130 if (TraceWorkGang) {
131 tty->print_cr("Running work gang %s task %s", name(), task->name());
132 }
133 // Tell all the workers to run a task.
134 assert(task != NULL, "Running a null task");
135 // Initialize.
136 _task = task;
137 _sequence_number += 1;
138 _started_workers = 0;
139 _finished_workers = 0;
140 // Tell the workers to get to work.
141 monitor()->notify_all();
142 // Wait for them to be finished
143 while (finished_workers() < no_of_parallel_workers) {
144 if (TraceWorkGang) {
145 tty->print_cr("Waiting in work gang %s: %u/%u finished sequence %d",
146 name(), finished_workers(), no_of_parallel_workers,
147 _sequence_number);
148 }
149 monitor()->wait(/* no_safepoint_check */ true);
150 }
151 _task = NULL;
152 if (TraceWorkGang) {
153 tty->print_cr("\nFinished work gang %s: %u/%u sequence %d",
154 name(), finished_workers(), no_of_parallel_workers,
155 _sequence_number);
156 Thread* me = Thread::current();
157 tty->print_cr(" T: " PTR_FORMAT " VM_thread: %d", p2i(me), me->is_VM_thread());
158 }
159 }
160
161 void WorkGang::internal_worker_poll(WorkData* data) const {
162 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
163 assert(data != NULL, "worker data is null");
164 data->set_task(task());
165 data->set_sequence_number(sequence_number());
166 }
167
168 void WorkGang::internal_note_start() {
169 assert(monitor()->owned_by_self(), "note_finish is an internal method");
170 _started_workers += 1;
171 }
172
173 void WorkGang::internal_note_finish() {
174 assert(monitor()->owned_by_self(), "note_finish is an internal method");
175 _finished_workers += 1;
176 }
177
178 // GangWorker methods.
179
180 AbstractGangWorker::AbstractGangWorker(AbstractWorkGang* gang, uint id) {
181 _gang = gang;
182 set_id(id);
183 set_name("%s#%d", gang->name(), id);
184 }
185
186 void AbstractGangWorker::run() {
187 initialize();
188 loop();
189 }
190
191 void AbstractGangWorker::initialize() {
192 this->initialize_thread_local_storage();
193 this->record_stack_base_and_size();
194 this->initialize_named_thread();
195 assert(_gang != NULL, "No gang to run in");
196 os::set_priority(this, NearMaxPriority);
197 if (TraceWorkGang) {
198 tty->print_cr("Running gang worker for gang %s id %u",
201 // The VM thread should not execute here because MutexLocker's are used
202 // as (opposed to MutexLockerEx's).
203 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
204 " of a work gang");
205 }
206
207 bool AbstractGangWorker::is_GC_task_thread() const {
208 return gang()->are_GC_task_threads();
209 }
210
211 bool AbstractGangWorker::is_ConcurrentGC_thread() const {
212 return gang()->are_ConcurrentGC_threads();
213 }
214
215 void AbstractGangWorker::print_on(outputStream* st) const {
216 st->print("\"%s\" ", name());
217 Thread::print_on(st);
218 st->cr();
219 }
220
221 void GangWorker::loop() {
222 int previous_sequence_number = 0;
223 Monitor* gang_monitor = gang()->monitor();
224 for ( ; ; ) {
225 WorkData data;
226 int part; // Initialized below.
227 {
228 // Grab the gang mutex.
229 MutexLocker ml(gang_monitor);
230 // Wait for something to do.
231 // Polling outside the while { wait } avoids missed notifies
232 // in the outer loop.
233 gang()->internal_worker_poll(&data);
234 if (TraceWorkGang) {
235 tty->print("Polled outside for work in gang %s worker %u",
236 gang()->name(), id());
237 tty->print(" sequence: %d (prev: %d)",
238 data.sequence_number(), previous_sequence_number);
239 if (data.task() != NULL) {
240 tty->print(" task: %s", data.task()->name());
241 } else {
242 tty->print(" task: NULL");
243 }
244 tty->cr();
245 }
246 for ( ; /* break */; ) {
247 // Check for new work.
248 if ((data.task() != NULL) &&
249 (data.sequence_number() != previous_sequence_number)) {
250 if (gang()->needs_more_workers()) {
251 gang()->internal_note_start();
252 gang_monitor->notify_all();
253 part = gang()->started_workers() - 1;
254 break;
255 }
256 }
257 // Nothing to do.
258 gang_monitor->wait(/* no_safepoint_check */ true);
259 gang()->internal_worker_poll(&data);
260 if (TraceWorkGang) {
261 tty->print("Polled inside for work in gang %s worker %u",
262 gang()->name(), id());
263 tty->print(" sequence: %d (prev: %d)",
264 data.sequence_number(), previous_sequence_number);
265 if (data.task() != NULL) {
266 tty->print(" task: %s", data.task()->name());
267 } else {
268 tty->print(" task: NULL");
269 }
270 tty->cr();
271 }
272 }
273 // Drop gang mutex.
274 }
275 if (TraceWorkGang) {
276 tty->print("Work for work gang %s id %u task %s part %d",
277 gang()->name(), id(), data.task()->name(), part);
278 }
279 assert(data.task() != NULL, "Got null task");
280 data.task()->work(part);
281 {
282 if (TraceWorkGang) {
283 tty->print("Finish for work gang %s id %u task %s part %d",
284 gang()->name(), id(), data.task()->name(), part);
285 }
286 // Grab the gang mutex.
287 MutexLocker ml(gang_monitor);
288 gang()->internal_note_finish();
289 // Tell the gang you are done.
290 gang_monitor->notify_all();
291 // Drop the gang mutex.
292 }
293 previous_sequence_number = data.sequence_number();
294 }
295 }
296
297 // *** WorkGangBarrierSync
298
299 WorkGangBarrierSync::WorkGangBarrierSync()
300 : _monitor(Mutex::safepoint, "work gang barrier sync", true,
301 Monitor::_safepoint_check_never),
302 _n_workers(0), _n_completed(0), _should_reset(false), _aborted(false) {
303 }
304
305 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
306 : _monitor(Mutex::safepoint, name, true, Monitor::_safepoint_check_never),
307 _n_workers(n_workers), _n_completed(0), _should_reset(false), _aborted(false) {
308 }
309
310 void WorkGangBarrierSync::set_n_workers(uint n_workers) {
311 _n_workers = n_workers;
312 _n_completed = 0;
313 _should_reset = false;
|
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/shared/workgroup.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "runtime/atomic.inline.hpp"
30 #include "runtime/os.hpp"
31 #include "runtime/semaphore.hpp"
32 #include "runtime/thread.inline.hpp"
33
34 // Definitions of WorkGang methods.
35
36 // The current implementation will exit if the allocation
37 // of any worker fails. Still, return a boolean so that
38 // a future implementation can possibly do a partial
39 // initialization of the workers and report such to the
40 // caller.
41 bool AbstractWorkGang::initialize_workers() {
42
43 if (TraceWorkGang) {
44 tty->print_cr("Constructing work gang %s with %d threads",
45 name(),
46 total_workers());
47 }
48 _workers = NEW_C_HEAP_ARRAY(AbstractGangWorker*, total_workers(), mtInternal);
49 if (_workers == NULL) {
50 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create GangWorker array.");
51 return false;
52 }
81 assert(result != NULL, "Indexing to null worker");
82 return result;
83 }
84
85 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
86 uint workers = total_workers();
87 for (uint i = 0; i < workers; i++) {
88 worker(i)->print_on(st);
89 st->cr();
90 }
91 }
92
93 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
94 assert(tc != NULL, "Null ThreadClosure");
95 uint workers = total_workers();
96 for (uint i = 0; i < workers; i++) {
97 tc->do_thread(worker(i));
98 }
99 }
100
101 // WorkGang dispatcher implemented with semaphores.
102 //
103 // Semaphores don't require the worker threads to re-claim the lock when they wake up.
104 // This helps lowering the latency when starting and stopping the worker threads.
105 class SemaphoreGangTaskDispatcher : public GangTaskDispatcher {
106 // The task currently being dispatched to the GangWorkers.
107 AbstractGangTask* _task;
108
109 volatile uint _started;
110 volatile uint _not_finished;
111
112 // Semaphore used to start the GangWorkers.
113 Semaphore* _start_semaphore;
114 // Semaphore used to notify the coordinator that all workers are done.
115 Semaphore* _end_semaphore;
116
117 public:
118 SemaphoreGangTaskDispatcher() :
119 _task(NULL),
120 _started(0),
121 _not_finished(0),
122 // Limit the semaphore value to the number of workers.
123 _start_semaphore(new Semaphore()),
124 _end_semaphore(new Semaphore())
125 { }
126
127 ~SemaphoreGangTaskDispatcher() {
128 delete _start_semaphore;
129 delete _end_semaphore;
130 }
131
132 void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) {
133 // No workers are allowed to read the state variables until they have been signaled.
134 _task = task;
135 _not_finished = num_workers;
136
137 // Dispatch 'num_workers' number of tasks.
138 _start_semaphore->signal(num_workers);
139
140 // Wait for the last worker to signal the coordinator.
141 _end_semaphore->wait();
142
143 // No workers are allowed to read the state variables after the coordinator has been signaled.
144 _task = NULL;
145 _started = 0;
146 _not_finished = 0;
147 }
148
149 WorkData worker_wait_for_task() {
150 // Wait for the coordinator to dispatch a task.
151 _start_semaphore->wait();
152
153 uint num_started = (uint) Atomic::add(1, (volatile jint*)&_started);
154
155 // Subtract one to get a zero-indexed worker id.
156 uint worker_id = num_started - 1;
157
158 return WorkData(_task, worker_id);
159 }
160
161 void worker_done_with_task() {
162 // Mark that the worker is done with the task.
163 // The worker is not allowed to read the state variables after this line.
164 uint not_finished = (uint) Atomic::add(-1, (volatile jint*)&_not_finished);
165
166 // The last worker signals to the coordinator that all work is completed.
167 if (not_finished == 0) {
168 _end_semaphore->signal();
169 }
170 }
171 };
172
173 class MutexGangTaskDispatcher : public GangTaskDispatcher {
174 AbstractGangTask* _task;
175
176 volatile uint _started;
177 volatile uint _finished;
178 volatile uint _num_workers;
179
180 Monitor* _monitor;
181
182 public:
183 MutexGangTaskDispatcher()
184 : _task(NULL),
185 _monitor(new Monitor(Monitor::leaf, "WorkGang dispatcher lock", false, Monitor::_safepoint_check_never)),
186 _started(0),
187 _finished(0),
188 _num_workers(0) {}
189
190 ~MutexGangTaskDispatcher() {
191 delete _monitor;
192 }
193
194 void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) {
195 MutexLockerEx ml(_monitor, Mutex::_no_safepoint_check_flag);
196
197 _task = task;
198 _num_workers = num_workers;
199
200 // Tell the workers to get to work.
201 _monitor->notify_all();
202
203 // Wait for them to finish.
204 while (_finished < _num_workers) {
205 _monitor->wait(/* no_safepoint_check */ true);
206 }
207
208 _task = NULL;
209 _num_workers = 0;
210 _started = 0;
211 _finished = 0;
212 }
213
214 WorkData worker_wait_for_task() {
215 MonitorLockerEx ml(_monitor, Mutex::_no_safepoint_check_flag);
216
217 while (_num_workers == 0 || _started == _num_workers) {
218 _monitor->wait(/* no_safepoint_check */ true);
219 }
220
221 _started++;
222
223 // Subtract one to get a zero-indexed worker id.
224 uint worker_id = _started - 1;
225
226 return WorkData(_task, worker_id);
227 }
228
229 void worker_done_with_task() {
230 MonitorLockerEx ml(_monitor, Mutex::_no_safepoint_check_flag);
231
232 _finished++;
233
234 if (_finished == _num_workers) {
235 // This will wake up all workers and not only the coordinator.
236 _monitor->notify_all();
237 }
238 }
239 };
240
241 static GangTaskDispatcher* create_dispatcher() {
242 if (UseSemaphoreGCThreadsSynchronization) {
243 return new SemaphoreGangTaskDispatcher();
244 }
245
246 return new MutexGangTaskDispatcher();
247 }
248
249 WorkGang::WorkGang(const char* name,
250 uint workers,
251 bool are_GC_task_threads,
252 bool are_ConcurrentGC_threads) :
253 AbstractWorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads),
254 _dispatcher(create_dispatcher())
255 { }
256
257 AbstractGangWorker* WorkGang::allocate_worker(uint worker_id) {
258 return new GangWorker(this, worker_id);
259 }
260
261 void WorkGang::run_task(AbstractGangTask* task) {
262 _dispatcher->coordinator_execute_on_workers(task, active_workers());
263 }
264
265 AbstractGangWorker::AbstractGangWorker(AbstractWorkGang* gang, uint id) {
266 _gang = gang;
267 set_id(id);
268 set_name("%s#%d", gang->name(), id);
269 }
270
271 void AbstractGangWorker::run() {
272 initialize();
273 loop();
274 }
275
276 void AbstractGangWorker::initialize() {
277 this->initialize_thread_local_storage();
278 this->record_stack_base_and_size();
279 this->initialize_named_thread();
280 assert(_gang != NULL, "No gang to run in");
281 os::set_priority(this, NearMaxPriority);
282 if (TraceWorkGang) {
283 tty->print_cr("Running gang worker for gang %s id %u",
286 // The VM thread should not execute here because MutexLocker's are used
287 // as (opposed to MutexLockerEx's).
288 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
289 " of a work gang");
290 }
291
292 bool AbstractGangWorker::is_GC_task_thread() const {
293 return gang()->are_GC_task_threads();
294 }
295
296 bool AbstractGangWorker::is_ConcurrentGC_thread() const {
297 return gang()->are_ConcurrentGC_threads();
298 }
299
300 void AbstractGangWorker::print_on(outputStream* st) const {
301 st->print("\"%s\" ", name());
302 Thread::print_on(st);
303 st->cr();
304 }
305
306 WorkData GangWorker::wait_for_task() {
307 return gang()->dispatcher()->worker_wait_for_task();
308 }
309
310 void GangWorker::signal_task_done() {
311 gang()->dispatcher()->worker_done_with_task();
312 }
313
314 void GangWorker::print_task_started(WorkData data) {
315 if (TraceWorkGang) {
316 tty->print_cr("Running work gang %s task %s worker %u", name(), data._task->name(), data._worker_id);
317 }
318 }
319
320 void GangWorker::print_task_done(WorkData data) {
321 if (TraceWorkGang) {
322 tty->print_cr("\nFinished work gang %s task %s worker %u", name(), data._task->name(), data._worker_id);
323 Thread* me = Thread::current();
324 tty->print_cr(" T: " PTR_FORMAT " VM_thread: %d", p2i(me), me->is_VM_thread());
325 }
326 }
327
328 void GangWorker::run_task(WorkData data) {
329 print_task_started(data);
330
331 data._task->work(data._worker_id);
332
333 print_task_done(data);
334 }
335
336 void GangWorker::loop() {
337 while (true) {
338 WorkData data = wait_for_task();
339
340 run_task(data);
341
342 signal_task_done();
343 }
344 }
345
346 // *** WorkGangBarrierSync
347
348 WorkGangBarrierSync::WorkGangBarrierSync()
349 : _monitor(Mutex::safepoint, "work gang barrier sync", true,
350 Monitor::_safepoint_check_never),
351 _n_workers(0), _n_completed(0), _should_reset(false), _aborted(false) {
352 }
353
354 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
355 : _monitor(Mutex::safepoint, name, true, Monitor::_safepoint_check_never),
356 _n_workers(n_workers), _n_completed(0), _should_reset(false), _aborted(false) {
357 }
358
359 void WorkGangBarrierSync::set_n_workers(uint n_workers) {
360 _n_workers = n_workers;
361 _n_completed = 0;
362 _should_reset = false;
|