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 collection_needs_workers (void)
130 return sgen_collection_is_concurrent ();
134 sgen_workers_enqueue_job (SgenThreadPoolJob *job)
136 if (!collection_needs_workers ()) {
137 job->func (NULL, job);
138 sgen_thread_pool_job_free (job);
142 sgen_thread_pool_job_enqueue (job);
146 sgen_workers_wait_for_jobs_finished (void)
148 sgen_thread_pool_wait_for_all_jobs ();
150 * If the idle task was never triggered or it finished before the last job did and
151 * then didn't get triggered again, we might end up in the situation of having
152 * something in the gray queue yet the idle task not working. The easiest way to
153 * make sure this doesn't stay that way is to just trigger it again after all jobs
156 sgen_workers_ensure_awake ();
160 workers_get_work (WorkerData *data)
162 SgenMajorCollector *major;
164 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
166 /* If we're concurrent, steal from the workers distribute gray queue. */
167 major = sgen_get_major_collector ();
168 if (major->is_concurrent) {
169 GrayQueueSection *section = sgen_section_gray_queue_dequeue (&workers_distribute_gray_queue);
171 sgen_gray_object_enqueue_section (&data->private_gray_queue, section);
176 /* Nobody to steal from */
177 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
182 concurrent_enqueue_check (GCObject *obj)
184 g_assert (sgen_concurrent_collection_in_progress ());
185 g_assert (!sgen_ptr_in_nursery (obj));
186 g_assert (SGEN_LOAD_VTABLE (obj));
190 init_private_gray_queue (WorkerData *data)
192 sgen_gray_object_queue_init (&data->private_gray_queue,
193 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
197 thread_pool_init_func (void *data_untyped)
199 WorkerData *data = data_untyped;
200 SgenMajorCollector *major = sgen_get_major_collector ();
202 sgen_client_thread_register_worker ();
204 if (!major->is_concurrent)
207 init_private_gray_queue (data);
211 continue_idle_func (void)
213 return state_is_working_or_enqueued (workers_state);
217 marker_idle_func (void *data_untyped)
219 WorkerData *data = data_untyped;
221 if (!continue_idle_func ())
224 SGEN_ASSERT (0, sgen_concurrent_collection_in_progress (), "The worker should only mark in concurrent collections.");
226 if (workers_state == STATE_WORK_ENQUEUED) {
227 set_state (STATE_WORK_ENQUEUED, STATE_WORKING);
228 SGEN_ASSERT (0, workers_state != STATE_NOT_WORKING, "How did we get from WORK ENQUEUED to NOT WORKING?");
231 if (!sgen_gray_object_queue_is_empty (&data->private_gray_queue) || workers_get_work (data)) {
232 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (idle_func_object_ops, &data->private_gray_queue);
234 SGEN_ASSERT (0, !sgen_gray_object_queue_is_empty (&data->private_gray_queue), "How is our gray queue empty if we just got work?");
236 sgen_drain_gray_stack (32, ctx);
238 worker_try_finish ();
243 init_distribute_gray_queue (void)
245 if (workers_distribute_gray_queue_inited) {
246 g_assert (sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue));
247 g_assert (workers_distribute_gray_queue.locked);
251 sgen_section_gray_queue_init (&workers_distribute_gray_queue, TRUE,
252 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
253 workers_distribute_gray_queue_inited = TRUE;
257 sgen_workers_init_distribute_gray_queue (void)
259 SGEN_ASSERT (0, sgen_get_major_collector ()->is_concurrent && collection_needs_workers (),
260 "Why should we init the distribute gray queue if we don't need it?");
261 init_distribute_gray_queue ();
265 sgen_workers_init (int num_workers)
268 void **workers_data_ptrs = alloca(num_workers * sizeof(void *));
270 if (!sgen_get_major_collector ()->is_concurrent) {
271 sgen_thread_pool_init (num_workers, thread_pool_init_func, NULL, NULL, NULL);
275 //g_print ("initing %d workers\n", num_workers);
277 workers_num = num_workers;
279 workers_data = sgen_alloc_internal_dynamic (sizeof (WorkerData) * num_workers, INTERNAL_MEM_WORKER_DATA, TRUE);
280 memset (workers_data, 0, sizeof (WorkerData) * num_workers);
282 init_distribute_gray_queue ();
284 for (i = 0; i < workers_num; ++i)
285 workers_data_ptrs [i] = (void *) &workers_data [i];
287 sgen_thread_pool_init (num_workers, thread_pool_init_func, marker_idle_func, continue_idle_func, workers_data_ptrs);
289 mono_counters_register ("# workers finished", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_workers_num_finished);
293 sgen_workers_start_all_workers (SgenObjectOperations *object_ops)
295 if (!collection_needs_workers ())
298 idle_func_object_ops = object_ops;
299 mono_memory_write_barrier ();
301 sgen_workers_ensure_awake ();
305 sgen_workers_join (void)
309 if (!collection_needs_workers ())
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 sgen_workers_all_done (void)
326 return workers_state == STATE_NOT_WORKING;
329 /* Must only be used for debugging */
331 sgen_workers_are_working (void)
333 return state_is_working_or_enqueued (workers_state);
337 sgen_workers_wait (void)
339 sgen_thread_pool_idle_wait ();
340 SGEN_ASSERT (0, sgen_workers_all_done (), "Why are the workers not done after we wait for them?");
343 SgenSectionGrayQueue*
344 sgen_workers_get_distribute_section_gray_queue (void)
346 return &workers_distribute_gray_queue;