Sat, 23 Nov 2013 12:25:13 +0100
8028128: Add a type safe alternative for working with counter based data
Reviewed-by: dholmes, egahlin
1 /*
2 * Copyright (c) 2002, 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
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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 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP
28 #include "memory/allocation.hpp"
29 #include "utilities/growableArray.hpp"
31 //
32 // psTasks.hpp is a collection of GCTasks used by the
33 // parallelScavenge collector.
34 //
36 class GCTask;
37 class OopClosure;
38 class OopStack;
39 class ObjectStartArray;
40 class ParallelTaskTerminator;
41 class MutableSpace;
42 class PSOldGen;
43 class Thread;
44 class VMThread;
46 //
47 // ScavengeRootsTask
48 //
49 // This task scans all the roots of a given type.
50 //
51 //
53 class ScavengeRootsTask : public GCTask {
54 public:
55 enum RootType {
56 universe = 1,
57 jni_handles = 2,
58 threads = 3,
59 object_synchronizer = 4,
60 flat_profiler = 5,
61 system_dictionary = 6,
62 class_loader_data = 7,
63 management = 8,
64 jvmti = 9,
65 code_cache = 10
66 };
67 private:
68 RootType _root_type;
69 public:
70 ScavengeRootsTask(RootType value) : _root_type(value) {}
72 char* name() { return (char *)"scavenge-roots-task"; }
74 virtual void do_it(GCTaskManager* manager, uint which);
75 };
77 //
78 // ThreadRootsTask
79 //
80 // This task scans the roots of a single thread. This task
81 // enables scanning of thread roots in parallel.
82 //
84 class ThreadRootsTask : public GCTask {
85 private:
86 JavaThread* _java_thread;
87 VMThread* _vm_thread;
88 public:
89 ThreadRootsTask(JavaThread* root) : _java_thread(root), _vm_thread(NULL) {}
90 ThreadRootsTask(VMThread* root) : _java_thread(NULL), _vm_thread(root) {}
92 char* name() { return (char *)"thread-roots-task"; }
94 virtual void do_it(GCTaskManager* manager, uint which);
95 };
97 //
98 // StealTask
99 //
100 // This task is used to distribute work to idle threads.
101 //
103 class StealTask : public GCTask {
104 private:
105 ParallelTaskTerminator* const _terminator;
106 public:
107 char* name() { return (char *)"steal-task"; }
109 StealTask(ParallelTaskTerminator* t);
111 ParallelTaskTerminator* terminator() { return _terminator; }
113 virtual void do_it(GCTaskManager* manager, uint which);
114 };
116 //
117 // OldToYoungRootsTask
118 //
119 // This task is used to scan old to young roots in parallel
120 //
121 // A GC thread executing this tasks divides the generation (old gen)
122 // into slices and takes a stripe in the slice as its part of the
123 // work.
124 //
125 // +===============+ slice 0
126 // | stripe 0 |
127 // +---------------+
128 // | stripe 1 |
129 // +---------------+
130 // | stripe 2 |
131 // +---------------+
132 // | stripe 3 |
133 // +===============+ slice 1
134 // | stripe 0 |
135 // +---------------+
136 // | stripe 1 |
137 // +---------------+
138 // | stripe 2 |
139 // +---------------+
140 // | stripe 3 |
141 // +===============+ slice 2
142 // ...
143 //
144 // A task is created for each stripe. In this case there are 4 tasks
145 // created. A GC thread first works on its stripe within slice 0
146 // and then moves to its stripe in the next slice until all stripes
147 // exceed the top of the generation. Note that having fewer GC threads
148 // than stripes works because all the tasks are executed so all stripes
149 // will be covered. In this example if 4 tasks have been created to cover
150 // all the stripes and there are only 3 threads, one of the threads will
151 // get the tasks with the 4th stripe. However, there is a dependence in
152 // CardTableExtension::scavenge_contents_parallel() on the number
153 // of tasks created. In scavenge_contents_parallel the distance
154 // to the next stripe is calculated based on the number of tasks.
155 // If the stripe width is ssize, a task's next stripe is at
156 // ssize * number_of_tasks (= slice_stride). In this case after
157 // finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1
158 // by adding slice_stride to the start of stripe 0 in slice 0 to get
159 // to the start of stride 0 in slice 1.
161 class OldToYoungRootsTask : public GCTask {
162 private:
163 PSOldGen* _gen;
164 HeapWord* _gen_top;
165 uint _stripe_number;
166 uint _stripe_total;
168 public:
169 OldToYoungRootsTask(PSOldGen *gen,
170 HeapWord* gen_top,
171 uint stripe_number,
172 uint stripe_total) :
173 _gen(gen),
174 _gen_top(gen_top),
175 _stripe_number(stripe_number),
176 _stripe_total(stripe_total) { }
178 char* name() { return (char *)"old-to-young-roots-task"; }
180 virtual void do_it(GCTaskManager* manager, uint which);
181 };
183 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP