1 /*
2 * Copyright (c) 2002, 2018, 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.
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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).
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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23 */
24
25 #ifndef SHARE_VM_GC_PARALLEL_PSTASKS_HPP
26 #define SHARE_VM_GC_PARALLEL_PSTASKS_HPP
27
28 #include "memory/allocation.hpp"
29 #include "utilities/growableArray.hpp"
30
31 //
32 // psTasks.hpp is a collection of GCTasks used by the
33 // parallelScavenge collector.
34 //
35
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;
45
46 //
47 // ScavengeRootsTask
48 //
49 // This task scans all the roots of a given type.
50 //
51 //
52
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 system_dictionary = 5,
61 class_loader_data = 6,
62 management = 7,
63 jvmti = 8,
64 code_cache = 9
65 };
66 private:
67 RootType _root_type;
68 public:
69 ScavengeRootsTask(RootType value) : _root_type(value) {}
70
71 char* name() { return (char *)"scavenge-roots-task"; }
72
73 virtual void do_it(GCTaskManager* manager, uint which);
74 };
75
76 //
77 // ThreadRootsTask
78 //
79 // This task scans the roots of a single thread. This task
80 // enables scanning of thread roots in parallel.
81 //
82
83 class ThreadRootsTask : public GCTask {
84 private:
85 JavaThread* _java_thread;
86 VMThread* _vm_thread;
87 public:
88 ThreadRootsTask(JavaThread* root) : _java_thread(root), _vm_thread(NULL) {}
89 ThreadRootsTask(VMThread* root) : _java_thread(NULL), _vm_thread(root) {}
90
91 char* name() { return (char *)"thread-roots-task"; }
92
93 virtual void do_it(GCTaskManager* manager, uint which);
94 };
95
96 //
97 // StealTask
98 //
99 // This task is used to distribute work to idle threads.
100 //
101
102 class StealTask : public GCTask {
103 private:
104 ParallelTaskTerminator* const _terminator;
105 public:
106 char* name() { return (char *)"steal-task"; }
107
108 StealTask(ParallelTaskTerminator* t);
109
110 ParallelTaskTerminator* terminator() { return _terminator; }
111
112 virtual void do_it(GCTaskManager* manager, uint which);
113 };
114
115 //
116 // OldToYoungRootsTask
117 //
118 // This task is used to scan old to young roots in parallel
119 //
120 // A GC thread executing this tasks divides the generation (old gen)
121 // into slices and takes a stripe in the slice as its part of the
122 // work.
123 //
124 // +===============+ slice 0
125 // | stripe 0 |
126 // +---------------+
127 // | stripe 1 |
128 // +---------------+
129 // | stripe 2 |
130 // +---------------+
131 // | stripe 3 |
132 // +===============+ slice 1
133 // | stripe 0 |
134 // +---------------+
135 // | stripe 1 |
136 // +---------------+
137 // | stripe 2 |
138 // +---------------+
139 // | stripe 3 |
140 // +===============+ slice 2
141 // ...
142 //
143 // A task is created for each stripe. In this case there are 4 tasks
144 // created. A GC thread first works on its stripe within slice 0
145 // and then moves to its stripe in the next slice until all stripes
146 // exceed the top of the generation. Note that having fewer GC threads
147 // than stripes works because all the tasks are executed so all stripes
148 // will be covered. In this example if 4 tasks have been created to cover
149 // all the stripes and there are only 3 threads, one of the threads will
150 // get the tasks with the 4th stripe. However, there is a dependence in
151 // PSCardTable::scavenge_contents_parallel() on the number
152 // of tasks created. In scavenge_contents_parallel the distance
153 // to the next stripe is calculated based on the number of tasks.
154 // If the stripe width is ssize, a task's next stripe is at
155 // ssize * number_of_tasks (= slice_stride). In this case after
156 // finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1
157 // by adding slice_stride to the start of stripe 0 in slice 0 to get
158 // to the start of stride 0 in slice 1.
159
160 class OldToYoungRootsTask : public GCTask {
161 private:
162 PSOldGen* _old_gen;
163 HeapWord* _gen_top;
164 uint _stripe_number;
165 uint _stripe_total;
166
167 public:
168 OldToYoungRootsTask(PSOldGen *old_gen,
169 HeapWord* gen_top,
170 uint stripe_number,
171 uint stripe_total) :
172 _old_gen(old_gen),
173 _gen_top(gen_top),
174 _stripe_number(stripe_number),
175 _stripe_total(stripe_total) { }
176
177 char* name() { return (char *)"old-to-young-roots-task"; }
178
179 virtual void do_it(GCTaskManager* manager, uint which);
180 };
181
182 #endif // SHARE_VM_GC_PARALLEL_PSTASKS_HPP