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