2 * sgen-workers.c: Worker threads for parallel and concurrent GC.
4 * Copyright 2001-2003 Ximian, Inc
5 * Copyright 2003-2010 Novell, Inc.
6 * Copyright (C) 2012 Xamarin Inc
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License 2.0 as published by the Free Software Foundation;
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License 2.0 along with this library; if not, write to the Free
19 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
27 #include "mono/sgen/sgen-gc.h"
28 #include "mono/sgen/sgen-workers.h"
29 #include "mono/sgen/sgen-thread-pool.h"
30 #include "mono/utils/mono-membar.h"
31 #include "mono/sgen/sgen-client.h"
33 static int workers_num;
34 static volatile gboolean forced_stop;
35 static WorkerData *workers_data;
37 static SgenSectionGrayQueue workers_distribute_gray_queue;
38 static gboolean workers_distribute_gray_queue_inited;
41 * Allowed transitions:
43 * | from \ to | NOT WORKING | WORKING | WORK ENQUEUED |
44 * |--------------------+-------------+---------+---------------+
45 * | NOT WORKING | - | - | main |
46 * | WORKING | worker | - | main |
47 * | WORK ENQUEUED | - | worker | - |
49 * The WORK ENQUEUED state guarantees that the worker thread will inspect the queue again at
50 * least once. Only after looking at the queue will it go back to WORKING, and then,
51 * eventually, to NOT WORKING. After enqueuing work the main thread transitions the state
52 * to WORK ENQUEUED. Signalling the worker thread to wake up is only necessary if the old
53 * state was NOT WORKING.
64 static volatile State workers_state;
66 static SgenObjectOperations * volatile idle_func_object_ops;
68 static guint64 stat_workers_num_finished;
71 set_state (State old_state, State new_state)
73 SGEN_ASSERT (0, old_state != new_state, "Why are we transitioning to the same state?");
74 if (new_state == STATE_NOT_WORKING)
75 SGEN_ASSERT (0, old_state == STATE_WORKING, "We can only transition to NOT WORKING from WORKING");
76 else if (new_state == STATE_WORKING)
77 SGEN_ASSERT (0, old_state == STATE_WORK_ENQUEUED, "We can only transition to WORKING from WORK ENQUEUED");
78 if (new_state == STATE_NOT_WORKING || new_state == STATE_WORKING)
79 SGEN_ASSERT (6, sgen_thread_pool_is_thread_pool_thread (mono_native_thread_id_get ()), "Only the worker thread is allowed to transition to NOT_WORKING or WORKING");
81 return InterlockedCompareExchange (&workers_state, new_state, old_state) == old_state;
85 state_is_working_or_enqueued (State state)
87 return state == STATE_WORKING || state == STATE_WORK_ENQUEUED;
91 sgen_workers_ensure_awake (void)
94 gboolean did_set_state;
97 old_state = workers_state;
99 if (old_state == STATE_WORK_ENQUEUED)
102 did_set_state = set_state (old_state, STATE_WORK_ENQUEUED);
103 } while (!did_set_state);
105 if (!state_is_working_or_enqueued (old_state))
106 sgen_thread_pool_idle_signal ();
110 worker_try_finish (void)
114 ++stat_workers_num_finished;
117 old_state = workers_state;
119 SGEN_ASSERT (0, old_state != STATE_NOT_WORKING, "How did we get from doing idle work to NOT WORKING without setting it ourselves?");
120 if (old_state == STATE_WORK_ENQUEUED)
122 SGEN_ASSERT (0, old_state == STATE_WORKING, "What other possibility is there?");
124 /* We are the last thread to go to sleep. */
125 } while (!set_state (old_state, STATE_NOT_WORKING));
127 binary_protocol_worker_finish (sgen_timestamp (), forced_stop);
131 sgen_workers_enqueue_job (SgenThreadPoolJob *job, gboolean enqueue)
134 job->func (NULL, job);
135 sgen_thread_pool_job_free (job);
139 sgen_thread_pool_job_enqueue (job);
143 sgen_workers_wait_for_jobs_finished (void)
145 sgen_thread_pool_wait_for_all_jobs ();
147 * If the idle task was never triggered or it finished before the last job did and
148 * then didn't get triggered again, we might end up in the situation of having
149 * something in the gray queue yet the idle task not working. The easiest way to
150 * make sure this doesn't stay that way is to just trigger it again after all jobs
153 sgen_workers_ensure_awake ();
157 workers_get_work (WorkerData *data)
159 SgenMajorCollector *major;
161 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
163 /* If we're concurrent, steal from the workers distribute gray queue. */
164 major = sgen_get_major_collector ();
165 if (major->is_concurrent) {
166 GrayQueueSection *section = sgen_section_gray_queue_dequeue (&workers_distribute_gray_queue);
168 sgen_gray_object_enqueue_section (&data->private_gray_queue, section);
173 /* Nobody to steal from */
174 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
179 concurrent_enqueue_check (GCObject *obj)
181 g_assert (sgen_concurrent_collection_in_progress ());
182 g_assert (!sgen_ptr_in_nursery (obj));
183 g_assert (SGEN_LOAD_VTABLE (obj));
187 init_private_gray_queue (WorkerData *data)
189 sgen_gray_object_queue_init (&data->private_gray_queue,
190 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
194 thread_pool_init_func (void *data_untyped)
196 WorkerData *data = (WorkerData *)data_untyped;
197 SgenMajorCollector *major = sgen_get_major_collector ();
199 sgen_client_thread_register_worker ();
201 if (!major->is_concurrent)
204 init_private_gray_queue (data);
208 continue_idle_func (void)
210 return state_is_working_or_enqueued (workers_state);
214 marker_idle_func (void *data_untyped)
216 WorkerData *data = (WorkerData *)data_untyped;
218 SGEN_ASSERT (0, continue_idle_func (), "Why are we called when we're not supposed to work?");
219 SGEN_ASSERT (0, sgen_concurrent_collection_in_progress (), "The worker should only mark in concurrent collections.");
221 if (workers_state == STATE_WORK_ENQUEUED) {
222 set_state (STATE_WORK_ENQUEUED, STATE_WORKING);
223 SGEN_ASSERT (0, workers_state != STATE_NOT_WORKING, "How did we get from WORK ENQUEUED to NOT WORKING?");
226 if (!forced_stop && (!sgen_gray_object_queue_is_empty (&data->private_gray_queue) || workers_get_work (data))) {
227 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (idle_func_object_ops, &data->private_gray_queue);
229 SGEN_ASSERT (0, !sgen_gray_object_queue_is_empty (&data->private_gray_queue), "How is our gray queue empty if we just got work?");
231 sgen_drain_gray_stack (ctx);
233 worker_try_finish ();
238 init_distribute_gray_queue (void)
240 if (workers_distribute_gray_queue_inited) {
241 g_assert (sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue));
242 g_assert (workers_distribute_gray_queue.locked);
246 sgen_section_gray_queue_init (&workers_distribute_gray_queue, TRUE,
247 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
248 workers_distribute_gray_queue_inited = TRUE;
252 sgen_workers_init_distribute_gray_queue (void)
254 SGEN_ASSERT (0, sgen_get_major_collector ()->is_concurrent,
255 "Why should we init the distribute gray queue if we don't need it?");
256 init_distribute_gray_queue ();
260 sgen_workers_init (int num_workers)
263 void **workers_data_ptrs = (void **)alloca(num_workers * sizeof(void *));
265 if (!sgen_get_major_collector ()->is_concurrent) {
266 sgen_thread_pool_init (num_workers, thread_pool_init_func, NULL, NULL, NULL);
270 //g_print ("initing %d workers\n", num_workers);
272 workers_num = num_workers;
274 workers_data = (WorkerData *)sgen_alloc_internal_dynamic (sizeof (WorkerData) * num_workers, INTERNAL_MEM_WORKER_DATA, TRUE);
275 memset (workers_data, 0, sizeof (WorkerData) * num_workers);
277 init_distribute_gray_queue ();
279 for (i = 0; i < workers_num; ++i)
280 workers_data_ptrs [i] = (void *) &workers_data [i];
282 sgen_thread_pool_init (num_workers, thread_pool_init_func, marker_idle_func, continue_idle_func, workers_data_ptrs);
284 mono_counters_register ("# workers finished", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_workers_num_finished);
288 sgen_workers_stop_all_workers (void)
292 sgen_thread_pool_wait_for_all_jobs ();
293 sgen_thread_pool_idle_wait ();
294 SGEN_ASSERT (0, workers_state == STATE_NOT_WORKING, "Can only signal enqueue work when in no work state");
298 sgen_workers_start_all_workers (SgenObjectOperations *object_ops)
301 idle_func_object_ops = object_ops;
302 mono_memory_write_barrier ();
304 sgen_workers_ensure_awake ();
308 sgen_workers_join (void)
312 sgen_thread_pool_wait_for_all_jobs ();
313 sgen_thread_pool_idle_wait ();
314 SGEN_ASSERT (0, workers_state == STATE_NOT_WORKING, "Can only signal enqueue work when in no work state");
316 /* At this point all the workers have stopped. */
318 SGEN_ASSERT (0, sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue), "Why is there still work left to do?");
319 for (i = 0; i < workers_num; ++i)
320 SGEN_ASSERT (0, sgen_gray_object_queue_is_empty (&workers_data [i].private_gray_queue), "Why is there still work left to do?");
324 * Can only be called if the workers are stopped.
325 * If we're stopped, there are also no pending jobs.
328 sgen_workers_have_idle_work (void)
332 SGEN_ASSERT (0, forced_stop && sgen_workers_all_done (), "Checking for idle work should only happen if the workers are stopped.");
334 if (!sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue))
337 for (i = 0; i < workers_num; ++i) {
338 if (!sgen_gray_object_queue_is_empty (&workers_data [i].private_gray_queue))
346 sgen_workers_all_done (void)
348 return workers_state == STATE_NOT_WORKING;
351 /* Must only be used for debugging */
353 sgen_workers_are_working (void)
355 return state_is_working_or_enqueued (workers_state);
358 SgenSectionGrayQueue*
359 sgen_workers_get_distribute_section_gray_queue (void)
361 return &workers_distribute_gray_queue;