1 /*
2 * Copyright (c) 2002, 2019, 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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12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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23 */
24
25 #ifndef SHARE_GC_PARALLEL_PSTASKS_HPP
26 #define SHARE_GC_PARALLEL_PSTASKS_HPP
27
28 #include "utilities/growableArray.hpp"
29
30 //
31 // psTasks.hpp is a collection of GCTasks used by the
32 // parallelScavenge collector.
33 //
34
35 class GCTask;
36 class OopClosure;
37 class OopStack;
38 class ObjectStartArray;
39 class ParallelTaskTerminator;
40 class MutableSpace;
41 class PSOldGen;
42 class Thread;
43 class VMThread;
44
45 //
46 // ScavengeRootsTask
47 //
48 // This task scans all the roots of a given type.
49 //
50 //
51
52 class ScavengeRootsTask : public GCTask {
53 public:
54 enum RootType {
55 universe = 1,
56 jni_handles = 2,
57 threads = 3,
58 object_synchronizer = 4,
59 system_dictionary = 5,
60 class_loader_data = 6,
61 management = 7,
62 jvmti = 8,
63 code_cache = 9
64 JVMCI_ONLY(COMMA jvmci = 10)
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 Thread* _thread;
86
87 public:
88 ThreadRootsTask(Thread* root) : _thread(root) {}
89
90 char* name() { return (char *)"thread-roots-task"; }
91
92 virtual void do_it(GCTaskManager* manager, uint which);
93 };
94
95 //
96 // StealTask
97 //
98 // This task is used to distribute work to idle threads.
99 //
100
101 class StealTask : public GCTask {
102 private:
103 ParallelTaskTerminator* const _terminator;
104 public:
105 char* name() { return (char *)"steal-task"; }
106
107 StealTask(ParallelTaskTerminator* t);
108
109 ParallelTaskTerminator* terminator() { return _terminator; }
110
111 virtual void do_it(GCTaskManager* manager, uint which);
112 };
113
114 //
115 // OldToYoungRootsTask
116 //
117 // This task is used to scan old to young roots in parallel
118 //
119 // A GC thread executing this tasks divides the generation (old gen)
120 // into slices and takes a stripe in the slice as its part of the
121 // work.
122 //
123 // +===============+ slice 0
124 // | stripe 0 |
125 // +---------------+
126 // | stripe 1 |
127 // +---------------+
128 // | stripe 2 |
129 // +---------------+
130 // | stripe 3 |
131 // +===============+ slice 1
132 // | stripe 0 |
133 // +---------------+
134 // | stripe 1 |
135 // +---------------+
136 // | stripe 2 |
137 // +---------------+
138 // | stripe 3 |
139 // +===============+ slice 2
140 // ...
141 //
142 // A task is created for each stripe. In this case there are 4 tasks
143 // created. A GC thread first works on its stripe within slice 0
144 // and then moves to its stripe in the next slice until all stripes
145 // exceed the top of the generation. Note that having fewer GC threads
146 // than stripes works because all the tasks are executed so all stripes
147 // will be covered. In this example if 4 tasks have been created to cover
148 // all the stripes and there are only 3 threads, one of the threads will
149 // get the tasks with the 4th stripe. However, there is a dependence in
150 // PSCardTable::scavenge_contents_parallel() on the number
151 // of tasks created. In scavenge_contents_parallel the distance
152 // to the next stripe is calculated based on the number of tasks.
153 // If the stripe width is ssize, a task's next stripe is at
154 // ssize * number_of_tasks (= slice_stride). In this case after
155 // finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1
156 // by adding slice_stride to the start of stripe 0 in slice 0 to get
157 // to the start of stride 0 in slice 1.
158
159 class OldToYoungRootsTask : public GCTask {
160 private:
161 PSOldGen* _old_gen;
162 HeapWord* _gen_top;
163 uint _stripe_number;
164 uint _stripe_total;
165
166 public:
167 OldToYoungRootsTask(PSOldGen *old_gen,
168 HeapWord* gen_top,
169 uint stripe_number,
170 uint stripe_total) :
171 _old_gen(old_gen),
172 _gen_top(gen_top),
173 _stripe_number(stripe_number),
174 _stripe_total(stripe_total) { }
175
176 char* name() { return (char *)"old-to-young-roots-task"; }
177
178 virtual void do_it(GCTaskManager* manager, uint which);
179 };
180
181 #endif // SHARE_GC_PARALLEL_PSTASKS_HPP