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 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
16 #include "mono/sgen/sgen-gc.h"
17 #include "mono/sgen/sgen-workers.h"
18 #include "mono/sgen/sgen-thread-pool.h"
19 #include "mono/utils/mono-membar.h"
20 #include "mono/sgen/sgen-client.h"
22 static int workers_num;
23 static volatile gboolean forced_stop;
24 static WorkerData *workers_data;
26 static SgenSectionGrayQueue workers_distribute_gray_queue;
27 static gboolean workers_distribute_gray_queue_inited;
30 * Allowed transitions:
32 * | from \ to | NOT WORKING | WORKING | WORK ENQUEUED |
33 * |--------------------+-------------+---------+---------------+
34 * | NOT WORKING | - | - | main |
35 * | WORKING | worker | - | main |
36 * | WORK ENQUEUED | - | worker | - |
38 * The WORK ENQUEUED state guarantees that the worker thread will inspect the queue again at
39 * least once. Only after looking at the queue will it go back to WORKING, and then,
40 * eventually, to NOT WORKING. After enqueuing work the main thread transitions the state
41 * to WORK ENQUEUED. Signalling the worker thread to wake up is only necessary if the old
42 * state was NOT WORKING.
53 static volatile State workers_state;
55 static SgenObjectOperations * volatile idle_func_object_ops;
56 static SgenThreadPoolJob * volatile preclean_job;
58 static guint64 stat_workers_num_finished;
61 set_state (State old_state, State new_state)
63 SGEN_ASSERT (0, old_state != new_state, "Why are we transitioning to the same state?");
64 if (new_state == STATE_NOT_WORKING)
65 SGEN_ASSERT (0, old_state == STATE_WORKING, "We can only transition to NOT WORKING from WORKING");
66 else if (new_state == STATE_WORKING)
67 SGEN_ASSERT (0, old_state == STATE_WORK_ENQUEUED, "We can only transition to WORKING from WORK ENQUEUED");
68 if (new_state == STATE_NOT_WORKING || new_state == STATE_WORKING)
69 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");
71 return InterlockedCompareExchange (&workers_state, new_state, old_state) == old_state;
75 state_is_working_or_enqueued (State state)
77 return state == STATE_WORKING || state == STATE_WORK_ENQUEUED;
81 sgen_workers_ensure_awake (void)
84 gboolean did_set_state;
87 old_state = workers_state;
89 if (old_state == STATE_WORK_ENQUEUED)
92 did_set_state = set_state (old_state, STATE_WORK_ENQUEUED);
93 } while (!did_set_state);
95 if (!state_is_working_or_enqueued (old_state))
96 sgen_thread_pool_idle_signal ();
100 worker_try_finish (void)
104 ++stat_workers_num_finished;
107 old_state = workers_state;
109 SGEN_ASSERT (0, old_state != STATE_NOT_WORKING, "How did we get from doing idle work to NOT WORKING without setting it ourselves?");
110 if (old_state == STATE_WORK_ENQUEUED)
112 SGEN_ASSERT (0, old_state == STATE_WORKING, "What other possibility is there?");
114 /* We are the last thread to go to sleep. */
115 } while (!set_state (old_state, STATE_NOT_WORKING));
117 binary_protocol_worker_finish (sgen_timestamp (), forced_stop);
121 sgen_workers_enqueue_job (SgenThreadPoolJob *job, gboolean enqueue)
124 job->func (NULL, job);
125 sgen_thread_pool_job_free (job);
129 sgen_thread_pool_job_enqueue (job);
133 sgen_workers_wait_for_jobs_finished (void)
135 sgen_thread_pool_wait_for_all_jobs ();
137 * If the idle task was never triggered or it finished before the last job did and
138 * then didn't get triggered again, we might end up in the situation of having
139 * something in the gray queue yet the idle task not working. The easiest way to
140 * make sure this doesn't stay that way is to just trigger it again after all jobs
143 sgen_workers_ensure_awake ();
147 workers_get_work (WorkerData *data)
149 SgenMajorCollector *major;
151 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
153 /* If we're concurrent, steal from the workers distribute gray queue. */
154 major = sgen_get_major_collector ();
155 if (major->is_concurrent) {
156 GrayQueueSection *section = sgen_section_gray_queue_dequeue (&workers_distribute_gray_queue);
158 sgen_gray_object_enqueue_section (&data->private_gray_queue, section);
163 /* Nobody to steal from */
164 g_assert (sgen_gray_object_queue_is_empty (&data->private_gray_queue));
169 concurrent_enqueue_check (GCObject *obj)
171 g_assert (sgen_concurrent_collection_in_progress ());
172 g_assert (!sgen_ptr_in_nursery (obj));
173 g_assert (SGEN_LOAD_VTABLE (obj));
177 init_private_gray_queue (WorkerData *data)
179 sgen_gray_object_queue_init (&data->private_gray_queue,
180 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
184 thread_pool_init_func (void *data_untyped)
186 WorkerData *data = (WorkerData *)data_untyped;
187 SgenMajorCollector *major = sgen_get_major_collector ();
189 sgen_client_thread_register_worker ();
191 if (!major->is_concurrent)
194 init_private_gray_queue (data);
198 continue_idle_func (void)
200 return state_is_working_or_enqueued (workers_state);
204 marker_idle_func (void *data_untyped)
206 WorkerData *data = (WorkerData *)data_untyped;
208 SGEN_ASSERT (0, continue_idle_func (), "Why are we called when we're not supposed to work?");
209 SGEN_ASSERT (0, sgen_concurrent_collection_in_progress (), "The worker should only mark in concurrent collections.");
211 if (workers_state == STATE_WORK_ENQUEUED) {
212 set_state (STATE_WORK_ENQUEUED, STATE_WORKING);
213 SGEN_ASSERT (0, workers_state != STATE_NOT_WORKING, "How did we get from WORK ENQUEUED to NOT WORKING?");
216 if (!forced_stop && (!sgen_gray_object_queue_is_empty (&data->private_gray_queue) || workers_get_work (data))) {
217 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (idle_func_object_ops, &data->private_gray_queue);
219 SGEN_ASSERT (0, !sgen_gray_object_queue_is_empty (&data->private_gray_queue), "How is our gray queue empty if we just got work?");
221 sgen_drain_gray_stack (ctx);
223 SgenThreadPoolJob *job = preclean_job;
225 sgen_thread_pool_job_enqueue (job);
228 worker_try_finish ();
234 init_distribute_gray_queue (void)
236 if (workers_distribute_gray_queue_inited) {
237 g_assert (sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue));
238 g_assert (workers_distribute_gray_queue.locked);
242 sgen_section_gray_queue_init (&workers_distribute_gray_queue, TRUE,
243 sgen_get_major_collector ()->is_concurrent ? concurrent_enqueue_check : NULL);
244 workers_distribute_gray_queue_inited = TRUE;
248 sgen_workers_init_distribute_gray_queue (void)
250 SGEN_ASSERT (0, sgen_get_major_collector ()->is_concurrent,
251 "Why should we init the distribute gray queue if we don't need it?");
252 init_distribute_gray_queue ();
256 sgen_workers_init (int num_workers)
259 void **workers_data_ptrs = (void **)alloca(num_workers * sizeof(void *));
261 if (!sgen_get_major_collector ()->is_concurrent) {
262 sgen_thread_pool_init (num_workers, thread_pool_init_func, NULL, NULL, NULL);
266 //g_print ("initing %d workers\n", num_workers);
268 workers_num = num_workers;
270 workers_data = (WorkerData *)sgen_alloc_internal_dynamic (sizeof (WorkerData) * num_workers, INTERNAL_MEM_WORKER_DATA, TRUE);
271 memset (workers_data, 0, sizeof (WorkerData) * num_workers);
273 init_distribute_gray_queue ();
275 for (i = 0; i < workers_num; ++i)
276 workers_data_ptrs [i] = (void *) &workers_data [i];
278 sgen_thread_pool_init (num_workers, thread_pool_init_func, marker_idle_func, continue_idle_func, workers_data_ptrs);
280 mono_counters_register ("# workers finished", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_workers_num_finished);
284 sgen_workers_stop_all_workers (void)
287 mono_memory_write_barrier ();
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, SgenThreadPoolJob *job)
299 idle_func_object_ops = object_ops;
301 mono_memory_write_barrier ();
303 sgen_workers_ensure_awake ();
307 sgen_workers_join (void)
311 sgen_thread_pool_wait_for_all_jobs ();
312 sgen_thread_pool_idle_wait ();
313 SGEN_ASSERT (0, workers_state == STATE_NOT_WORKING, "Can only signal enqueue work when in no work state");
315 /* At this point all the workers have stopped. */
317 SGEN_ASSERT (0, sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue), "Why is there still work left to do?");
318 for (i = 0; i < workers_num; ++i)
319 SGEN_ASSERT (0, sgen_gray_object_queue_is_empty (&workers_data [i].private_gray_queue), "Why is there still work left to do?");
323 * Can only be called if the workers are stopped.
324 * If we're stopped, there are also no pending jobs.
327 sgen_workers_have_idle_work (void)
331 SGEN_ASSERT (0, forced_stop && sgen_workers_all_done (), "Checking for idle work should only happen if the workers are stopped.");
333 if (!sgen_section_gray_queue_is_empty (&workers_distribute_gray_queue))
336 for (i = 0; i < workers_num; ++i) {
337 if (!sgen_gray_object_queue_is_empty (&workers_data [i].private_gray_queue))
345 sgen_workers_all_done (void)
347 return workers_state == STATE_NOT_WORKING;
350 /* Must only be used for debugging */
352 sgen_workers_are_working (void)
354 return state_is_working_or_enqueued (workers_state);
357 SgenSectionGrayQueue*
358 sgen_workers_get_distribute_section_gray_queue (void)
360 return &workers_distribute_gray_queue;