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
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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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 class FlexibleGangTask: public AbstractGangTask {
65 int _actual_size; // size of gang obtained
66 protected:
67 int _requested_size; // size of gang requested
68 public:
69 FlexibleGangTask(const char* name): AbstractGangTask(name),
70 _requested_size(0) {}
71
72 // The abstract work method.
73 // The argument tells you which member of the gang you are.
74 virtual void work(int i) = 0;
75
76 int requested_size() const { return _requested_size; }
77 int actual_size() const { return _actual_size; }
78
79 void set_requested_size(int sz) { _requested_size = sz; }
80 void set_actual_size(int sz) { _actual_size = sz; }
81 };
82
83 // An abstract task to be worked on by a flexible work gang,
84 // and where the workers will periodically yield, usually
85 // in response to some condition that is signalled by means
86 // that are specific to the task at hand.
87 // You subclass this to supply your own work() method.
88 // A second feature of this kind of work gang is that
89 // it allows for the signalling of certain exceptional
90 // conditions that may be encountered during the performance
91 // of the task and that may require the task at hand to be
92 // `aborted' forthwith. Finally, these gangs are `flexible'
93 // in that they can operate at partial capacity with some
94 // gang workers waiting on the bench; in other words, the
95 // size of the active worker pool can flex (up to an apriori
96 // maximum) in response to task requests at certain points.
97 // The last part (the flexible part) has not yet been fully
98 // fleshed out and is a work in progress.
99 class YieldingFlexibleGangTask: public FlexibleGangTask {
100 Status _status;
101 YieldingFlexibleWorkGang* _gang;
102
103 protected:
104 // Constructor and desctructor: only construct subclasses.
105 YieldingFlexibleGangTask(const char* name): FlexibleGangTask(name),
106 _status(INACTIVE),
107 _gang(NULL) { }
108
109 virtual ~YieldingFlexibleGangTask() { }
110
111 friend class YieldingFlexibleWorkGang;
112 friend class YieldingFlexibleGangWorker;
113 NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
114 return true;
115 })
116
117 void set_status(Status s) {
118 _status = s;
119 }
120 YieldingFlexibleWorkGang* gang() {
121 return _gang;
122 }
123 void set_gang(YieldingFlexibleWorkGang* gang) {
124 assert(_gang == NULL || gang == NULL, "Clobber without intermediate reset?");
125 _gang = gang;
126 }
127
128 public:
129 // The abstract work method.
130 // The argument tells you which member of the gang you are.
131 virtual void work(int i) = 0;
132
133 // Subclasses should call the parent's yield() method
134 // after having done any work specific to the subclass.
135 virtual void yield();
136
137 // An abstract method supplied by
138 // a concrete sub-class which is used by the coordinator
139 // to do any "central yielding" work.
140 virtual void coordinator_yield() = 0;
141
142 // Subclasses should call the parent's abort() method
143 // after having done any work specific to the sunbclass.
144 virtual void abort();
145
146 Status status() const { return _status; }
147 bool yielding() const { return _status == YIELDING; }
148 bool yielded() const { return _status == YIELDED; }
149 bool completed() const { return _status == COMPLETED; }
150 bool aborted() const { return _status == ABORTED; }
151 bool active() const { return _status == ACTIVE; }
152 };
153 // Class YieldingWorkGang: A subclass of WorkGang.
154 // In particular, a YieldingWorkGang is made up of
155 // YieldingGangWorkers, and provides infrastructure
156 // supporting yielding to the "GangOverseer",
157 // being the thread that orchestrates the WorkGang via run_task().
158 class YieldingFlexibleWorkGang: public FlexibleWorkGang {
159 // Here's the public interface to this class.
160 public:
161 // Constructor and destructor.
162 YieldingFlexibleWorkGang(const char* name, int workers,
163 bool are_GC_task_threads);
164
165 YieldingFlexibleGangTask* yielding_task() const {
166 assert(task() == NULL || task()->is_YieldingFlexibleGang_task(),
167 "Incorrect cast");
168 return (YieldingFlexibleGangTask*)task();
169 }
170 // Allocate a worker and return a pointer to it.
171 GangWorker* allocate_worker(int which);
172
173 // Run a task; returns when the task is done, or the workers yield,
174 // or the task is aborted, or the work gang is terminated via stop().
175 // A task that has been yielded can be continued via this same interface
176 // by using the same task repeatedly as the argument to the call.
177 // It is expected that the YieldingFlexibleGangTask carries the appropriate
178 // continuation information used by workers to continue the task
179 // from its last yield point. Thus, a completed task will return
180 // immediately with no actual work having been done by the workers.
181 void run_task(AbstractGangTask* task) {
182 guarantee(false, "Use start_task instead");
183 }
184 void start_task(YieldingFlexibleGangTask* new_task);
185 void continue_task(YieldingFlexibleGangTask* gang_task);
186
187 // Abort a currently running task, if any; returns when all the workers
188 // have stopped working on the current task and have returned to their
189 // waiting stations.
190 void abort_task();
191
192 // Yield: workers wait at their current working stations
193 // until signalled to proceed by the overseer.
194 void yield();
195
196 // Abort: workers are expected to return to their waiting
197 // stations, whence they are ready for the next task dispatched
198 // by the overseer.
199 void abort();
200
201 private:
202 int _active_workers;
203 int _yielded_workers;
204 void wait_for_gang();
205
206 public:
207 // Accessors for fields
208 int active_workers() const {
209 return _active_workers;
210 }
211
212 // Accessors for fields
213 int yielded_workers() const {
214 return _yielded_workers;
215 }
216
217 private:
218 friend class YieldingFlexibleGangWorker;
219 void reset(); // NYI
220 };
221
222 #endif // SHARE_VM_UTILITIES_YIELDINGWORKGROUP_HPP