1 /*
2 * Copyright (c) 2005, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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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).
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23 */
24
25 #ifndef SHARE_VM_GC_CMS_YIELDINGWORKGROUP_HPP
26 #define SHARE_VM_GC_CMS_YIELDINGWORKGROUP_HPP
27
28 #include "gc/shared/workgroup.hpp"
29 #include "utilities/macros.hpp"
30
31 // Forward declarations
32 class YieldingFlexibleGangTask;
33 class YieldingFlexibleWorkGang;
34
35 // Status of tasks
36 enum Status {
37 INACTIVE,
38 ACTIVE,
39 YIELDING,
40 YIELDED,
41 ABORTING,
42 ABORTED,
43 COMPLETING,
44 COMPLETED
45 };
46
47 class YieldingWorkData: public StackObj {
48 // This would be a struct, but I want accessor methods.
49 private:
50 AbstractGangTask* _task;
51 int _sequence_number;
52 public:
53 // Constructor and destructor
54 YieldingWorkData() : _task(NULL), _sequence_number(0) {}
55 ~YieldingWorkData() {}
56
57 // Accessors and modifiers
58 AbstractGangTask* task() const { return _task; }
59 void set_task(AbstractGangTask* value) { _task = value; }
60 int sequence_number() const { return _sequence_number; }
61 void set_sequence_number(int value) { _sequence_number = value; }
62
63 YieldingFlexibleGangTask* yf_task() const {
64 return (YieldingFlexibleGangTask*)_task;
65 }
66 };
67
68 // Class YieldingFlexibleGangWorker:
69 // Several instances of this class run in parallel as workers for a gang.
70 class YieldingFlexibleGangWorker: public AbstractGangWorker {
71 public:
72 YieldingFlexibleGangWorker(YieldingFlexibleWorkGang* gang, int id);
73
74 public:
75 YieldingFlexibleWorkGang* yf_gang() const
76 { return (YieldingFlexibleWorkGang*)gang(); }
77
78 protected: // Override from parent class
79 virtual void loop();
80 };
81
82 class FlexibleGangTask: public AbstractGangTask {
83 int _actual_size; // size of gang obtained
84 protected:
85 int _requested_size; // size of gang requested
86 public:
87 FlexibleGangTask(const char* name): AbstractGangTask(name),
88 _requested_size(0) {}
89
90 // The abstract work method.
91 // The argument tells you which member of the gang you are.
92 virtual void work(uint worker_id) = 0;
93
94 int requested_size() const { return _requested_size; }
95 int actual_size() const { return _actual_size; }
96
97 void set_requested_size(int sz) { _requested_size = sz; }
98 void set_actual_size(int sz) { _actual_size = sz; }
99 };
100
101 // An abstract task to be worked on by a flexible work gang,
102 // and where the workers will periodically yield, usually
103 // in response to some condition that is signalled by means
104 // that are specific to the task at hand.
105 // You subclass this to supply your own work() method.
106 // A second feature of this kind of work gang is that
107 // it allows for the signalling of certain exceptional
108 // conditions that may be encountered during the performance
109 // of the task and that may require the task at hand to be
110 // `aborted' forthwith. Finally, these gangs are `flexible'
111 // in that they can operate at partial capacity with some
112 // gang workers waiting on the bench; in other words, the
113 // size of the active worker pool can flex (up to an apriori
114 // maximum) in response to task requests at certain points.
115 // The last part (the flexible part) has not yet been fully
116 // fleshed out and is a work in progress.
117 class YieldingFlexibleGangTask: public FlexibleGangTask {
118 Status _status;
119 YieldingFlexibleWorkGang* _gang;
120
121 protected:
122 // Constructor and desctructor: only construct subclasses.
123 YieldingFlexibleGangTask(const char* name): FlexibleGangTask(name),
124 _status(INACTIVE),
125 _gang(NULL) { }
126
127 ~YieldingFlexibleGangTask() { }
128
129 friend class YieldingFlexibleWorkGang;
130 friend class YieldingFlexibleGangWorker;
131 NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
132 return true;
133 })
134
135 void set_status(Status s) {
136 _status = s;
137 }
138 YieldingFlexibleWorkGang* gang() {
139 return _gang;
140 }
141 void set_gang(YieldingFlexibleWorkGang* gang) {
142 assert(_gang == NULL || gang == NULL, "Clobber without intermediate reset?");
143 _gang = gang;
144 }
145
146 public:
147 // The abstract work method.
148 // The argument tells you which member of the gang you are.
149 virtual void work(uint worker_id) = 0;
150
151 // Subclasses should call the parent's yield() method
152 // after having done any work specific to the subclass.
153 virtual void yield();
154
155 // An abstract method supplied by
156 // a concrete sub-class which is used by the coordinator
157 // to do any "central yielding" work.
158 virtual void coordinator_yield() = 0;
159
160 // Subclasses should call the parent's abort() method
161 // after having done any work specific to the sunbclass.
162 virtual void abort();
163
164 Status status() const { return _status; }
165 bool yielding() const { return _status == YIELDING; }
166 bool yielded() const { return _status == YIELDED; }
167 bool completed() const { return _status == COMPLETED; }
168 bool aborted() const { return _status == ABORTED; }
169 bool active() const { return _status == ACTIVE; }
170
171 // This method configures the task for proper termination.
172 // Some tasks do not have any requirements on termination
173 // and may inherit this method that does nothing. Some
174 // tasks do some coordination on termination and override
175 // this method to implement that coordination.
176 virtual void set_for_termination(uint active_workers) {}
177 };
178 // Class YieldingWorkGang: A subclass of WorkGang.
179 // In particular, a YieldingWorkGang is made up of
180 // YieldingGangWorkers, and provides infrastructure
181 // supporting yielding to the "GangOverseer",
182 // being the thread that orchestrates the WorkGang via run_task().
183 class YieldingFlexibleWorkGang: public AbstractWorkGang {
184 // Here's the public interface to this class.
185 public:
186 // Constructor and destructor.
187 YieldingFlexibleWorkGang(const char* name, uint workers,
188 bool are_GC_task_threads);
189
190 YieldingFlexibleGangTask* yielding_task() const {
191 assert(task() == NULL || task()->is_YieldingFlexibleGang_task(),
192 "Incorrect cast");
193 return (YieldingFlexibleGangTask*)task();
194 }
195 // Allocate a worker and return a pointer to it.
196 AbstractGangWorker* allocate_worker(uint which);
197
198 // Run a task; returns when the task is done, or the workers yield,
199 // or the task is aborted.
200 // A task that has been yielded can be continued via this same interface
201 // by using the same task repeatedly as the argument to the call.
202 // It is expected that the YieldingFlexibleGangTask carries the appropriate
203 // continuation information used by workers to continue the task
204 // from its last yield point. Thus, a completed task will return
205 // immediately with no actual work having been done by the workers.
206 void run_task(AbstractGangTask* task) {
207 guarantee(false, "Use start_task instead");
208 }
209 void start_task(YieldingFlexibleGangTask* new_task);
210 void continue_task(YieldingFlexibleGangTask* gang_task);
211
212 // Abort a currently running task, if any; returns when all the workers
213 // have stopped working on the current task and have returned to their
214 // waiting stations.
215 void abort_task();
216
217 // Yield: workers wait at their current working stations
218 // until signalled to proceed by the overseer.
219 void yield();
220
221 // Abort: workers are expected to return to their waiting
222 // stations, whence they are ready for the next task dispatched
223 // by the overseer.
224 void abort();
225
226 private:
227 uint _yielded_workers;
228 void wait_for_gang();
229
230 public:
231 // Accessors for fields
232 uint yielded_workers() const {
233 return _yielded_workers;
234 }
235
236 private:
237 friend class YieldingFlexibleGangWorker;
238 void reset(); // NYI
239
240
241 // The monitor which protects these data,
242 // and notifies of changes in it.
243 Monitor* _monitor;
244 // Accessors for fields
245 Monitor* monitor() const {
246 return _monitor;
247 }
248
249 // The number of started workers.
250 uint _started_workers;
251 // The number of finished workers.
252 uint _finished_workers;
253
254 uint started_workers() const {
255 return _started_workers;
256 }
257 uint finished_workers() const {
258 return _finished_workers;
259 }
260
261 // A sequence number for the current task.
262 int _sequence_number;
263 int sequence_number() const {
264 return _sequence_number;
265 }
266
267 YieldingFlexibleGangTask* _task;
268 YieldingFlexibleGangTask* task() const {
269 return _task;
270 }
271
272 void internal_worker_poll(YieldingWorkData* data) const;
273 void internal_note_start();
274 void internal_note_finish();
275 };
276
277 #endif // SHARE_VM_GC_CMS_YIELDINGWORKGROUP_HPP