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 WorkerData *workers_data;
36 static SgenSectionGrayQueue workers_distribute_gray_queue;
37 static gboolean workers_distribute_gray_queue_inited;
40 * Allowed transitions:
42 * | from \ to | NOT WORKING | WORKING | WORK ENQUEUED |
43 * |--------------------+-------------+---------+---------------+
44 * | NOT WORKING | - | - | main |
45 * | WORKING | worker | - | main |
46 * | WORK ENQUEUED | - | worker | - |
48 * The WORK ENQUEUED state guarantees that the worker thread will inspect the queue again at
49 * least once. Only after looking at the queue will it go back to WORKING, and then,
50 * eventually, to NOT WORKING. After enqueuing work the main thread transitions the state
51 * to WORK ENQUEUED. Signalling the worker thread to wake up is only necessary if the old
52 * state was NOT WORKING.
63 static volatile State workers_state;
65 static SgenObjectOperations * volatile idle_func_object_ops;
67 static guint64 stat_workers_num_finished;
70 set_state (State old_state, State new_state)
72 SGEN_ASSERT (0, old_state != new_state, "Why are we transitioning to the same state?");
73 if (new_state == STATE_NOT_WORKING)
74 SGEN_ASSERT (0, old_state == STATE_WORKING, "We can only transition to NOT WORKING from WORKING");
75 else if (new_state == STATE_WORKING)
76 SGEN_ASSERT (0, old_state == STATE_WORK_ENQUEUED, "We can only transition to WORKING from WORK ENQUEUED");
77 if (new_state == STATE_NOT_WORKING || new_state == STATE_WORKING)
78 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");
80 return InterlockedCompareExchange (&workers_state, new_state, old_state) == old_state;
84 state_is_working_or_enqueued (State state)
86 return state == STATE_WORKING || state == STATE_WORK_ENQUEUED;
90 sgen_workers_ensure_awake (void)
93 gboolean did_set_state;
96 old_state = workers_state;
98 if (old_state == STATE_WORK_ENQUEUED)
101 did_set_state = set_state (old_state, STATE_WORK_ENQUEUED);
102 } while (!did_set_state);
104 if (!state_is_working_or_enqueued (old_state))
105 sgen_thread_pool_idle_signal ();
109 worker_try_finish (void)
113 ++stat_workers_num_finished;
116 old_state = workers_state;
118 SGEN_ASSERT (0, old_state != STATE_NOT_WORKING, "How did we get from doing idle work to NOT WORKING without setting it ourselves?");
119 if (old_state == STATE_WORK_ENQUEUED)
121 SGEN_ASSERT (0, old_state == STATE_WORKING, "What other possibility is there?");
123 /* We are the last thread to go to sleep. */
124 } while (!set_state (old_state, STATE_NOT_WORKING));
128 sgen_workers_enqueue_job (SgenThreadPoolJob *job, gboolean enqueue)
131 job->func (NULL, job);
132 sgen_thread_pool_job_free (job);
136 sgen_thread_pool_job_enqueue (job);
140 sgen_workers_wait_for_jobs_finished (void)
142 sgen_thread_pool_wait_for_all_jobs ();
144 * If the idle task was never triggered or it finished before the last job did and
145 * then didn't get triggered again, we might end up in the situation of having
146 * something in the gray queue yet the idle task not working. The easiest way to
147 * make sure this doesn't stay that way is to just trigger it again after all jobs
150 sgen_workers_ensure_awake ();
154 workers_get_work (WorkerData *data)
156 SgenMajorCollector *major;
158 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
160 /* If we're concurrent, steal from the workers distribute gray queue. */
161 major = sgen_get_major_collector ();
162 if (major->is_concurrent) {
163 GrayQueueSection *section = sgen_section_gray_queue_dequeue (&workers_distribute_gray_queue);
165 sgen_gray_object_enqueue_section (&data->private_gray_queue, section);
170 /* Nobody to steal from */
171 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
176 concurrent_enqueue_check (GCObject *obj)
178 g_assert (sgen_concurrent_collection_in_progress ());
179 g_assert (!sgen_ptr_in_nursery (obj));
180 g_assert (SGEN_LOAD_VTABLE (obj));
184 init_private_gray_queue (WorkerData *data)
186 sgen_gray_object_queue_init (&data->private_gray_queue,
187 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
191 thread_pool_init_func (void *data_untyped)
193 WorkerData *data = data_untyped;
194 SgenMajorCollector *major = sgen_get_major_collector ();
196 sgen_client_thread_register_worker ();
198 if (!major->is_concurrent)
201 init_private_gray_queue (data);
205 continue_idle_func (void)
207 return state_is_working_or_enqueued (workers_state);
211 marker_idle_func (void *data_untyped)
213 WorkerData *data = data_untyped;
215 SGEN_ASSERT (0, continue_idle_func (), "Why are we called when we're not supposed to work?");
216 SGEN_ASSERT (0, sgen_concurrent_collection_in_progress (), "The worker should only mark in concurrent collections.");
218 if (workers_state == STATE_WORK_ENQUEUED) {
219 set_state (STATE_WORK_ENQUEUED, STATE_WORKING);
220 SGEN_ASSERT (0, workers_state != STATE_NOT_WORKING, "How did we get from WORK ENQUEUED to NOT WORKING?");
223 if (!sgen_gray_object_queue_is_empty (&data->private_gray_queue) || workers_get_work (data)) {
224 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (idle_func_object_ops, &data->private_gray_queue);
226 SGEN_ASSERT (0, !sgen_gray_object_queue_is_empty (&data->private_gray_queue), "How is our gray queue empty if we just got work?");
228 sgen_drain_gray_stack (ctx);
230 worker_try_finish ();
235 init_distribute_gray_queue (void)
237 if (workers_distribute_gray_queue_inited) {
238 g_assert (sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue));
239 g_assert (workers_distribute_gray_queue.locked);
243 sgen_section_gray_queue_init (&workers_distribute_gray_queue, TRUE,
244 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
245 workers_distribute_gray_queue_inited = TRUE;
249 sgen_workers_init_distribute_gray_queue (void)
251 SGEN_ASSERT (0, sgen_get_major_collector ()->is_concurrent,
252 "Why should we init the distribute gray queue if we don't need it?");
253 init_distribute_gray_queue ();
257 sgen_workers_init (int num_workers)
260 void **workers_data_ptrs = alloca(num_workers * sizeof(void *));
262 if (!sgen_get_major_collector ()->is_concurrent) {
263 sgen_thread_pool_init (num_workers, thread_pool_init_func, NULL, NULL, NULL);
267 //g_print ("initing %d workers\n", num_workers);
269 workers_num = num_workers;
271 workers_data = sgen_alloc_internal_dynamic (sizeof (WorkerData) * num_workers, INTERNAL_MEM_WORKER_DATA, TRUE);
272 memset (workers_data, 0, sizeof (WorkerData) * num_workers);
274 init_distribute_gray_queue ();
276 for (i = 0; i < workers_num; ++i)
277 workers_data_ptrs [i] = (void *) &workers_data [i];
279 sgen_thread_pool_init (num_workers, thread_pool_init_func, marker_idle_func, continue_idle_func, workers_data_ptrs);
281 mono_counters_register ("# workers finished", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_workers_num_finished);
285 sgen_workers_start_all_workers (SgenObjectOperations *object_ops)
287 idle_func_object_ops = object_ops;
288 mono_memory_write_barrier ();
290 sgen_workers_ensure_awake ();
294 sgen_workers_join (void)
298 sgen_thread_pool_wait_for_all_jobs ();
299 sgen_thread_pool_idle_wait ();
300 SGEN_ASSERT (0, workers_state == STATE_NOT_WORKING, "Can only signal enqueue work when in no work state");
302 /* At this point all the workers have stopped. */
304 SGEN_ASSERT (0, sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue), "Why is there still work left to do?");
305 for (i = 0; i < workers_num; ++i)
306 SGEN_ASSERT (0, sgen_gray_object_queue_is_empty (&workers_data [i].private_gray_queue), "Why is there still work left to do?");
310 sgen_workers_all_done (void)
312 return workers_state == STATE_NOT_WORKING;
315 /* Must only be used for debugging */
317 sgen_workers_are_working (void)
319 return state_is_working_or_enqueued (workers_state);
323 sgen_workers_wait (void)
325 sgen_thread_pool_idle_wait ();
326 SGEN_ASSERT (0, sgen_workers_all_done (), "Why are the workers not done after we wait for them?");
329 SgenSectionGrayQueue*
330 sgen_workers_get_distribute_section_gray_queue (void)
332 return &workers_distribute_gray_queue;