1/*
2 * Copyright (c) 2002, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25#ifndef SHARE_GC_SHARED_WORKGROUP_HPP
26#define SHARE_GC_SHARED_WORKGROUP_HPP
27
28#include "memory/allocation.hpp"
29#include "runtime/globals.hpp"
30#include "runtime/thread.hpp"
31#include "gc/shared/gcId.hpp"
32#include "logging/log.hpp"
33#include "utilities/debug.hpp"
34#include "utilities/globalDefinitions.hpp"
35
36// Task class hierarchy:
37// AbstractGangTask
38//
39// Gang/Group class hierarchy:
40// AbstractWorkGang
41// WorkGang
42// YieldingFlexibleWorkGang (defined in another file)
43//
44// Worker class hierarchy:
45// AbstractGangWorker (subclass of WorkerThread)
46// GangWorker
47// YieldingFlexibleGangWorker (defined in another file)
48
49// Forward declarations of classes defined here
50
51class AbstractGangWorker;
52class Semaphore;
53class WorkGang;
54
55// An abstract task to be worked on by a gang.
56// You subclass this to supply your own work() method
57class AbstractGangTask {
58 const char* _name;
59 const uint _gc_id;
60
61 public:
62 explicit AbstractGangTask(const char* name) :
63 _name(name),
64 _gc_id(GCId::current_or_undefined())
65 {}
66
67 // The abstract work method.
68 // The argument tells you which member of the gang you are.
69 virtual void work(uint worker_id) = 0;
70
71 // Debugging accessor for the name.
72 const char* name() const { return _name; }
73 const uint gc_id() const { return _gc_id; }
74};
75
76struct WorkData {
77 AbstractGangTask* _task;
78 uint _worker_id;
79 WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
80};
81
82// Interface to handle the synchronization between the coordinator thread and the worker threads,
83// when a task is dispatched out to the worker threads.
84class GangTaskDispatcher : public CHeapObj<mtGC> {
85 public:
86 virtual ~GangTaskDispatcher() {}
87
88 // Coordinator API.
89
90 // Distributes the task out to num_workers workers.
91 // Returns when the task has been completed by all workers.
92 virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;
93
94 // Worker API.
95
96 // Waits for a task to become available to the worker.
97 // Returns when the worker has been assigned a task.
98 virtual WorkData worker_wait_for_task() = 0;
99
100 // Signal to the coordinator that the worker is done with the assigned task.
101 virtual void worker_done_with_task() = 0;
102};
103
104// The work gang is the collection of workers to execute tasks.
105// The number of workers run for a task is "_active_workers"
106// while "_total_workers" is the number of available of workers.
107class AbstractWorkGang : public CHeapObj<mtInternal> {
108 protected:
109 // The array of worker threads for this gang.
110 AbstractGangWorker** _workers;
111 // The count of the number of workers in the gang.
112 uint _total_workers;
113 // The currently active workers in this gang.
114 uint _active_workers;
115 // The count of created workers in the gang.
116 uint _created_workers;
117 // Printing support.
118 const char* _name;
119
120 ~AbstractWorkGang() {}
121
122 private:
123 // Initialize only instance data.
124 const bool _are_GC_task_threads;
125 const bool _are_ConcurrentGC_threads;
126
127 void set_thread(uint worker_id, AbstractGangWorker* worker) {
128 _workers[worker_id] = worker;
129 }
130
131 public:
132 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
133 _workers(NULL),
134 _total_workers(workers),
135 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
136 _created_workers(0),
137 _name(name),
138 _are_GC_task_threads(are_GC_task_threads),
139 _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
140 { }
141
142 // Initialize workers in the gang. Return true if initialization succeeded.
143 void initialize_workers();
144
145 bool are_GC_task_threads() const { return _are_GC_task_threads; }
146 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
147
148 uint total_workers() const { return _total_workers; }
149
150 uint created_workers() const {
151 return _created_workers;
152 }
153
154 virtual uint active_workers() const {
155 assert(_active_workers <= _total_workers,
156 "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);
157 return _active_workers;
158 }
159
160 uint update_active_workers(uint v) {
161 assert(v <= _total_workers,
162 "Trying to set more workers active than there are");
163 _active_workers = MIN2(v, _total_workers);
164 add_workers(false /* exit_on_failure */);
165 assert(v != 0, "Trying to set active workers to 0");
166 log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers);
167 return _active_workers;
168 }
169
170 // Add GC workers as needed.
171 void add_workers(bool initializing);
172
173 // Add GC workers as needed to reach the specified number of workers.
174 void add_workers(uint active_workers, bool initializing);
175
176 // Return the Ith worker.
177 AbstractGangWorker* worker(uint i) const;
178
179 // Base name (without worker id #) of threads.
180 const char* group_name() { return name(); }
181
182 void threads_do(ThreadClosure* tc) const;
183
184 // Create a GC worker and install it into the work gang.
185 virtual AbstractGangWorker* install_worker(uint which);
186
187 // Debugging.
188 const char* name() const { return _name; }
189
190 // Printing
191 void print_worker_threads_on(outputStream *st) const;
192 void print_worker_threads() const {
193 print_worker_threads_on(tty);
194 }
195
196 protected:
197 virtual AbstractGangWorker* allocate_worker(uint which) = 0;
198};
199
200// An class representing a gang of workers.
201class WorkGang: public AbstractWorkGang {
202 // To get access to the GangTaskDispatcher instance.
203 friend class GangWorker;
204
205 GangTaskDispatcher* const _dispatcher;
206 GangTaskDispatcher* dispatcher() const {
207 return _dispatcher;
208 }
209
210public:
211 WorkGang(const char* name,
212 uint workers,
213 bool are_GC_task_threads,
214 bool are_ConcurrentGC_threads);
215
216 ~WorkGang();
217
218 // Run a task using the current active number of workers, returns when the task is done.
219 virtual void run_task(AbstractGangTask* task);
220 // Run a task with the given number of workers, returns
221 // when the task is done. The number of workers must be at most the number of
222 // active workers. Additional workers may be created if an insufficient
223 // number currently exists.
224 void run_task(AbstractGangTask* task, uint num_workers);
225
226protected:
227 virtual AbstractGangWorker* allocate_worker(uint which);
228};
229
230// Several instances of this class run in parallel as workers for a gang.
231class AbstractGangWorker: public WorkerThread {
232public:
233 AbstractGangWorker(AbstractWorkGang* gang, uint id);
234
235 // The only real method: run a task for the gang.
236 virtual void run();
237 // Predicate for Thread
238 virtual bool is_GC_task_thread() const;
239 virtual bool is_ConcurrentGC_thread() const;
240 // Printing
241 void print_on(outputStream* st) const;
242 virtual void print() const;
243
244protected:
245 AbstractWorkGang* _gang;
246
247 virtual void initialize();
248 virtual void loop() = 0;
249
250 AbstractWorkGang* gang() const { return _gang; }
251};
252
253class GangWorker: public AbstractGangWorker {
254public:
255 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
256
257protected:
258 virtual void loop();
259
260private:
261 WorkData wait_for_task();
262 void run_task(WorkData work);
263 void signal_task_done();
264
265 WorkGang* gang() const { return (WorkGang*)_gang; }
266};
267
268// A class that acts as a synchronisation barrier. Workers enter
269// the barrier and must wait until all other workers have entered
270// before any of them may leave.
271
272class WorkGangBarrierSync : public StackObj {
273protected:
274 Monitor _monitor;
275 uint _n_workers;
276 uint _n_completed;
277 bool _should_reset;
278 bool _aborted;
279
280 Monitor* monitor() { return &_monitor; }
281 uint n_workers() { return _n_workers; }
282 uint n_completed() { return _n_completed; }
283 bool should_reset() { return _should_reset; }
284 bool aborted() { return _aborted; }
285
286 void zero_completed() { _n_completed = 0; }
287 void inc_completed() { _n_completed++; }
288 void set_aborted() { _aborted = true; }
289 void set_should_reset(bool v) { _should_reset = v; }
290
291public:
292 WorkGangBarrierSync();
293 WorkGangBarrierSync(uint n_workers, const char* name);
294
295 // Set the number of workers that will use the barrier.
296 // Must be called before any of the workers start running.
297 void set_n_workers(uint n_workers);
298
299 // Enter the barrier. A worker that enters the barrier will
300 // not be allowed to leave until all other threads have
301 // also entered the barrier or the barrier is aborted.
302 // Returns false if the barrier was aborted.
303 bool enter();
304
305 // Aborts the barrier and wakes up any threads waiting for
306 // the barrier to complete. The barrier will remain in the
307 // aborted state until the next call to set_n_workers().
308 void abort();
309};
310
311// A class to manage claiming of subtasks within a group of tasks. The
312// subtasks will be identified by integer indices, usually elements of an
313// enumeration type.
314
315class SubTasksDone: public CHeapObj<mtInternal> {
316 volatile uint* _tasks;
317 uint _n_tasks;
318 volatile uint _threads_completed;
319#ifdef ASSERT
320 volatile uint _claimed;
321#endif
322
323 // Set all tasks to unclaimed.
324 void clear();
325
326public:
327 // Initializes "this" to a state in which there are "n" tasks to be
328 // processed, none of the which are originally claimed. The number of
329 // threads doing the tasks is initialized 1.
330 SubTasksDone(uint n);
331
332 // True iff the object is in a valid state.
333 bool valid();
334
335 // Attempt to claim the task "t", returning true if successful,
336 // false if it has already been claimed. The task "t" is required
337 // to be within the range of "this".
338 bool try_claim_task(uint t);
339
340 // The calling thread asserts that it has attempted to claim all the
341 // tasks that it will try to claim. Every thread in the parallel task
342 // must execute this. (When the last thread does so, the task array is
343 // cleared.)
344 //
345 // n_threads - Number of threads executing the sub-tasks.
346 void all_tasks_completed(uint n_threads);
347
348 // Destructor.
349 ~SubTasksDone();
350};
351
352// As above, but for sequential tasks, i.e. instead of claiming
353// sub-tasks from a set (possibly an enumeration), claim sub-tasks
354// in sequential order. This is ideal for claiming dynamically
355// partitioned tasks (like striding in the parallel remembered
356// set scanning). Note that unlike the above class this is
357// a stack object - is there any reason for it not to be?
358
359class SequentialSubTasksDone : public StackObj {
360protected:
361 uint _n_tasks; // Total number of tasks available.
362 volatile uint _n_claimed; // Number of tasks claimed.
363 // _n_threads is used to determine when a sub task is done.
364 // See comments on SubTasksDone::_n_threads
365 uint _n_threads; // Total number of parallel threads.
366 volatile uint _n_completed; // Number of completed threads.
367
368 void clear();
369
370public:
371 SequentialSubTasksDone() {
372 clear();
373 }
374 ~SequentialSubTasksDone() {}
375
376 // True iff the object is in a valid state.
377 bool valid();
378
379 // number of tasks
380 uint n_tasks() const { return _n_tasks; }
381
382 // Get/set the number of parallel threads doing the tasks to t.
383 // Should be called before the task starts but it is safe
384 // to call this once a task is running provided that all
385 // threads agree on the number of threads.
386 uint n_threads() { return _n_threads; }
387 void set_n_threads(uint t) { _n_threads = t; }
388
389 // Set the number of tasks to be claimed to t. As above,
390 // should be called before the tasks start but it is safe
391 // to call this once a task is running provided all threads
392 // agree on the number of tasks.
393 void set_n_tasks(uint t) { _n_tasks = t; }
394
395 // Attempt to claim the next unclaimed task in the sequence,
396 // returning true if successful, with t set to the index of the
397 // claimed task. Returns false if there are no more unclaimed tasks
398 // in the sequence.
399 bool try_claim_task(uint& t);
400
401 // The calling thread asserts that it has attempted to claim
402 // all the tasks it possibly can in the sequence. Every thread
403 // claiming tasks must promise call this. Returns true if this
404 // is the last thread to complete so that the thread can perform
405 // cleanup if necessary.
406 bool all_tasks_completed();
407};
408
409#endif // SHARE_GC_SHARED_WORKGROUP_HPP
410