1 /*
2 * Copyright (c) 2005, 2010, 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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25 #ifndef SHARE_VM_UTILITIES_YIELDINGWORKGROUP_HPP
26 #define SHARE_VM_UTILITIES_YIELDINGWORKGROUP_HPP
27
28 #ifndef SERIALGC
29 #include "utilities/workgroup.hpp"
30 #endif
31
32
33 // Forward declarations
34 class YieldingFlexibleWorkGang;
35
36 // Status of tasks
37 enum Status {
38 INACTIVE,
39 ACTIVE,
40 YIELDING,
41 YIELDED,
42 ABORTING,
43 ABORTED,
44 COMPLETING,
45 COMPLETED
46 };
47
48 // Class YieldingFlexibleGangWorker:
49 // Several instances of this class run in parallel as workers for a gang.
50 class YieldingFlexibleGangWorker: public GangWorker {
51 public:
52 // Ctor
53 YieldingFlexibleGangWorker(AbstractWorkGang* gang, int id) :
54 GangWorker(gang, id) { }
55
56 public:
57 YieldingFlexibleWorkGang* yf_gang() const
58 { return (YieldingFlexibleWorkGang*)gang(); }
59
60 protected: // Override from parent class
61 virtual void loop();
62 };
63
64 // An abstract task to be worked on by a flexible work gang,
65 // and where the workers will periodically yield, usually
66 // in response to some condition that is signalled by means
67 // that are specific to the task at hand.
68 // You subclass this to supply your own work() method.
69 // A second feature of this kind of work gang is that
70 // it allows for the signalling of certain exceptional
71 // conditions that may be encountered during the performance
72 // of the task and that may require the task at hand to be
73 // `aborted' forthwith. Finally, these gangs are `flexible'
74 // in that they can operate at partial capacity with some
75 // gang workers waiting on the bench; in other words, the
76 // size of the active worker pool can flex (up to an apriori
77 // maximum) in response to task requests at certain points.
78 // The last part (the flexible part) has not yet been fully
79 // fleshed out and is a work in progress.
80 class YieldingFlexibleGangTask: public AbstractGangTask {
81 Status _status;
82 YieldingFlexibleWorkGang* _gang;
83 int _actual_size; // size of gang obtained
84
85 protected:
86 int _requested_size; // size of gang requested
87
88 // Constructor and desctructor: only construct subclasses.
89 YieldingFlexibleGangTask(const char* name): AbstractGangTask(name),
90 _status(INACTIVE),
91 _gang(NULL),
92 _requested_size(0) { }
93
94 virtual ~YieldingFlexibleGangTask() { }
95
96 friend class YieldingFlexibleWorkGang;
97 friend class YieldingFlexibleGangWorker;
98 NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
99 return true;
100 })
101
102 void set_status(Status s) {
103 _status = s;
104 }
105 YieldingFlexibleWorkGang* gang() {
106 return _gang;
107 }
108 void set_gang(YieldingFlexibleWorkGang* gang) {
109 assert(_gang == NULL || gang == NULL, "Clobber without intermediate reset?");
110 _gang = gang;
111 }
112
113 public:
114 // The abstract work method.
115 // The argument tells you which member of the gang you are.
116 virtual void work(int i) = 0;
117
118 // Subclasses should call the parent's yield() method
119 // after having done any work specific to the subclass.
120 virtual void yield();
121
122 // An abstract method supplied by
123 // a concrete sub-class which is used by the coordinator
124 // to do any "central yielding" work.
125 virtual void coordinator_yield() = 0;
126
127 // Subclasses should call the parent's abort() method
128 // after having done any work specific to the sunbclass.
129 virtual void abort();
130
131 Status status() const { return _status; }
132 bool yielded() const { return _status == YIELDED; }
133 bool completed() const { return _status == COMPLETED; }
134 bool aborted() const { return _status == ABORTED; }
135 bool active() const { return _status == ACTIVE; }
136
137 int requested_size() const { return _requested_size; }
138 int actual_size() const { return _actual_size; }
139
140 void set_requested_size(int sz) { _requested_size = sz; }
141 void set_actual_size(int sz) { _actual_size = sz; }
142 };
143
144 // Class YieldingWorkGang: A subclass of WorkGang.
145 // In particular, a YieldingWorkGang is made up of
146 // YieldingGangWorkers, and provides infrastructure
147 // supporting yielding to the "GangOverseer",
148 // being the thread that orchestrates the WorkGang via run_task().
149 class YieldingFlexibleWorkGang: public AbstractWorkGang {
150 // Here's the public interface to this class.
151 public:
152 // Constructor and destructor.
153 YieldingFlexibleWorkGang(const char* name, int workers,
154 bool are_GC_task_threads);
155
156 YieldingFlexibleGangTask* yielding_task() const {
157 assert(task() == NULL || task()->is_YieldingFlexibleGang_task(),
158 "Incorrect cast");
159 return (YieldingFlexibleGangTask*)task();
160 }
161 // Run a task; returns when the task is done, or the workers yield,
162 // or the task is aborted, or the work gang is terminated via stop().
163 // A task that has been yielded can be continued via this same interface
164 // by using the same task repeatedly as the argument to the call.
165 // It is expected that the YieldingFlexibleGangTask carries the appropriate
166 // continuation information used by workers to continue the task
167 // from its last yield point. Thus, a completed task will return
168 // immediately with no actual work having been done by the workers.
169 void run_task(AbstractGangTask* task) {
170 guarantee(false, "Use start_task instead");
171 }
172 void start_task(YieldingFlexibleGangTask* new_task);
173 void continue_task(YieldingFlexibleGangTask* gang_task);
174
175 // Abort a currently running task, if any; returns when all the workers
176 // have stopped working on the current task and have returned to their
177 // waiting stations.
178 void abort_task();
179
180 // Yield: workers wait at their current working stations
181 // until signalled to proceed by the overseer.
182 void yield();
183
184 // Abort: workers are expected to return to their waiting
185 // stations, whence they are ready for the next task dispatched
186 // by the overseer.
187 void abort();
188
189 private:
190 // The currently active workers in this gang.
191 // This is a number that is dynamically adjusted by
192 // the run_task() method at each subsequent invocation,
193 // using data in the YieldingFlexibleGangTask.
194 int _active_workers;
195 int _yielded_workers;
196 void wait_for_gang();
197
198 public:
199 // Accessors for fields
200 int active_workers() const {
201 return _active_workers;
202 }
203
204 int yielded_workers() const {
205 return _yielded_workers;
206 }
207
208 private:
209 friend class YieldingFlexibleGangWorker;
210 void reset(); // NYI
211 };
212
213 #endif // SHARE_VM_UTILITIES_YIELDINGWORKGROUP_HPP