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));
129 sgen_workers_enqueue_job (SgenThreadPoolJob *job, gboolean enqueue)
132 job->func (NULL, job);
133 sgen_thread_pool_job_free (job);
137 sgen_thread_pool_job_enqueue (job);
141 sgen_workers_wait_for_jobs_finished (void)
143 sgen_thread_pool_wait_for_all_jobs ();
145 * If the idle task was never triggered or it finished before the last job did and
146 * then didn't get triggered again, we might end up in the situation of having
147 * something in the gray queue yet the idle task not working. The easiest way to
148 * make sure this doesn't stay that way is to just trigger it again after all jobs
151 sgen_workers_ensure_awake ();
155 workers_get_work (WorkerData *data)
157 SgenMajorCollector *major;
159 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
161 /* If we're concurrent, steal from the workers distribute gray queue. */
162 major = sgen_get_major_collector ();
163 if (major->is_concurrent) {
164 GrayQueueSection *section = sgen_section_gray_queue_dequeue (&workers_distribute_gray_queue);
166 sgen_gray_object_enqueue_section (&data->private_gray_queue, section);
171 /* Nobody to steal from */
172 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
177 concurrent_enqueue_check (GCObject *obj)
179 g_assert (sgen_concurrent_collection_in_progress ());
180 g_assert (!sgen_ptr_in_nursery (obj));
181 g_assert (SGEN_LOAD_VTABLE (obj));
185 init_private_gray_queue (WorkerData *data)
187 sgen_gray_object_queue_init (&data->private_gray_queue,
188 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
192 thread_pool_init_func (void *data_untyped)
194 WorkerData *data = (WorkerData *)data_untyped;
195 SgenMajorCollector *major = sgen_get_major_collector ();
197 sgen_client_thread_register_worker ();
199 if (!major->is_concurrent)
202 init_private_gray_queue (data);
206 continue_idle_func (void)
208 return state_is_working_or_enqueued (workers_state);
212 marker_idle_func (void *data_untyped)
214 WorkerData *data = (WorkerData *)data_untyped;
216 SGEN_ASSERT (0, continue_idle_func (), "Why are we called when we're not supposed to work?");
217 SGEN_ASSERT (0, sgen_concurrent_collection_in_progress (), "The worker should only mark in concurrent collections.");
219 if (workers_state == STATE_WORK_ENQUEUED) {
220 set_state (STATE_WORK_ENQUEUED, STATE_WORKING);
221 SGEN_ASSERT (0, workers_state != STATE_NOT_WORKING, "How did we get from WORK ENQUEUED to NOT WORKING?");
224 if (!forced_stop && (!sgen_gray_object_queue_is_empty (&data->private_gray_queue) || workers_get_work (data))) {
225 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (idle_func_object_ops, &data->private_gray_queue);
227 SGEN_ASSERT (0, !sgen_gray_object_queue_is_empty (&data->private_gray_queue), "How is our gray queue empty if we just got work?");
229 sgen_drain_gray_stack (ctx);
231 worker_try_finish ();
236 init_distribute_gray_queue (void)
238 if (workers_distribute_gray_queue_inited) {
239 g_assert (sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue));
240 g_assert (workers_distribute_gray_queue.locked);
244 sgen_section_gray_queue_init (&workers_distribute_gray_queue, TRUE,
245 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
246 workers_distribute_gray_queue_inited = TRUE;
250 sgen_workers_init_distribute_gray_queue (void)
252 SGEN_ASSERT (0, sgen_get_major_collector ()->is_concurrent,
253 "Why should we init the distribute gray queue if we don't need it?");
254 init_distribute_gray_queue ();
258 sgen_workers_init (int num_workers)
261 void **workers_data_ptrs = (void **)alloca(num_workers * sizeof(void *));
263 if (!sgen_get_major_collector ()->is_concurrent) {
264 sgen_thread_pool_init (num_workers, thread_pool_init_func, NULL, NULL, NULL);
268 //g_print ("initing %d workers\n", num_workers);
270 workers_num = num_workers;
272 workers_data = (WorkerData *)sgen_alloc_internal_dynamic (sizeof (WorkerData) * num_workers, INTERNAL_MEM_WORKER_DATA, TRUE);
273 memset (workers_data, 0, sizeof (WorkerData) * num_workers);
275 init_distribute_gray_queue ();
277 for (i = 0; i < workers_num; ++i)
278 workers_data_ptrs [i] = (void *) &workers_data [i];
280 sgen_thread_pool_init (num_workers, thread_pool_init_func, marker_idle_func, continue_idle_func, workers_data_ptrs);
282 mono_counters_register ("# workers finished", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_workers_num_finished);
286 sgen_workers_stop_all_workers (void)
290 sgen_thread_pool_wait_for_all_jobs ();
291 sgen_thread_pool_idle_wait ();
292 SGEN_ASSERT (0, workers_state == STATE_NOT_WORKING, "Can only signal enqueue work when in no work state");
296 sgen_workers_start_all_workers (SgenObjectOperations *object_ops)
299 idle_func_object_ops = object_ops;
300 mono_memory_write_barrier ();
302 sgen_workers_ensure_awake ();
306 sgen_workers_join (void)
310 sgen_thread_pool_wait_for_all_jobs ();
311 sgen_thread_pool_idle_wait ();
312 SGEN_ASSERT (0, workers_state == STATE_NOT_WORKING, "Can only signal enqueue work when in no work state");
314 /* At this point all the workers have stopped. */
316 SGEN_ASSERT (0, sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue), "Why is there still work left to do?");
317 for (i = 0; i < workers_num; ++i)
318 SGEN_ASSERT (0, sgen_gray_object_queue_is_empty (&workers_data [i].private_gray_queue), "Why is there still work left to do?");
322 * Can only be called if the workers are stopped.
323 * If we're stopped, there are also no pending jobs.
326 sgen_workers_have_idle_work (void)
330 SGEN_ASSERT (0, forced_stop && sgen_workers_all_done (), "Checking for idle work should only happen if the workers are stopped.");
332 if (!sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue))
335 for (i = 0; i < workers_num; ++i) {
336 if (!sgen_gray_object_queue_is_empty (&workers_data [i].private_gray_queue))
344 sgen_workers_all_done (void)
346 return workers_state == STATE_NOT_WORKING;
349 /* Must only be used for debugging */
351 sgen_workers_are_working (void)
353 return state_is_working_or_enqueued (workers_state);
356 SgenSectionGrayQueue*
357 sgen_workers_get_distribute_section_gray_queue (void)
359 return &workers_distribute_gray_queue;