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comparison: src/share/vm/gc_implementation/g1/g1AllocRegion.hpp

src/share/vm/gc_implementation/g1/g1AllocRegion.hpp

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1 /*
2 * Copyright (c) 2011, 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.
18 *
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.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
27
28 #include "gc_implementation/g1/heapRegion.hpp"
29
30 class G1CollectedHeap;
31
32 // 0 -> no tracing, 1 -> basic tracing, 2 -> basic + allocation tracing
33 #define G1_ALLOC_REGION_TRACING 0
34
35 class ar_ext_msg;
36
37 // A class that holds a region that is active in satisfying allocation
38 // requests, potentially issued in parallel. When the active region is
39 // full it will be retired it replaced with a new one. The
40 // implementation assumes that fast-path allocations will be lock-free
41 // and a lock will need to be taken when the active region needs to be
42 // replaced.
43
44 class G1AllocRegion VALUE_OBJ_CLASS_SPEC {
45 friend class ar_ext_msg;
46
47 private:
48 // The active allocating region we are currently allocating out
49 // of. The invariant is that if this object is initialized (i.e.,
50 // init() has been called and release() has not) then _alloc_region
51 // is either an active allocating region or the dummy region (i.e.,
52 // it can never be NULL) and this object can be used to satisfy
53 // allocation requests. If this object is not initialized
54 // (i.e. init() has not been called or release() has been called)
55 // then _alloc_region is NULL and this object should not be used to
56 // satisfy allocation requests (it was done this way to force the
57 // correct use of init() and release()).
58 HeapRegion* _alloc_region;
59
60 // When we set up a new active region we save its used bytes in this
61 // field so that, when we retire it, we can calculate how much space
62 // we allocated in it.
63 size_t _used_bytes_before;
64
65 // Specifies whether the allocate calls will do BOT updates or not.
66 bool _bot_updates;
67
68 // Useful for debugging and tracing.
69 const char* _name;
70
71 // A dummy region (i.e., it's been allocated specially for this
72 // purpose and it is not part of the heap) that is full (i.e., top()
73 // == end()). When we don't have a valid active region we make
74 // _alloc_region point to this. This allows us to skip checking
75 // whether the _alloc_region is NULL or not.
76 static HeapRegion* _dummy_region;
77
78 // Some of the methods below take a bot_updates parameter. Its value
79 // should be the same as the _bot_updates field. The idea is that
80 // the parameter will be a constant for a particular alloc region
81 // and, given that these methods will be hopefully inlined, the
82 // compiler should compile out the test.
83
84 // Perform a non-MT-safe allocation out of the given region.
85 static inline HeapWord* allocate(HeapRegion* alloc_region,
86 size_t word_size,
87 bool bot_updates);
88
89 // Perform a MT-safe allocation out of the given region.
90 static inline HeapWord* par_allocate(HeapRegion* alloc_region,
91 size_t word_size,
92 bool bot_updates);
93
94 // Ensure that the region passed as a parameter has been filled up
95 // so that noone else can allocate out of it any more.
96 static void fill_up_remaining_space(HeapRegion* alloc_region,
97 bool bot_updates);
98
99 // Retire the active allocating region. If fill_up is true then make
100 // sure that the region is full before we retire it so that noone
101 // else can allocate out of it.
102 void retire(bool fill_up);
103
104 // Allocate a new active region and use it to perform a word_size
105 // allocation. The force parameter will be passed on to
106 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
107 // to allocate a new region even if the max has been reached.
108 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
109
110 void fill_in_ext_msg(ar_ext_msg* msg, const char* message);
111
112 protected:
113 // For convenience as subclasses use it.
114 static G1CollectedHeap* _g1h;
115
116 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
117 virtual void retire_region(HeapRegion* alloc_region,
118 size_t allocated_bytes) = 0;
119
120 G1AllocRegion(const char* name, bool bot_updates);
121
122 public:
123 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
124
125 HeapRegion* get() const {
126 // Make sure that the dummy region does not escape this class.
127 return (_alloc_region == _dummy_region) ? NULL : _alloc_region;
128 }
129
130 // The following two are the building blocks for the allocation method.
131
132 // First-level allocation: Should be called without holding a
133 // lock. It will try to allocate lock-free out of the active region,
134 // or return NULL if it was unable to.
135 inline HeapWord* attempt_allocation(size_t word_size, bool bot_updates);
136
137 // Second-level allocation: Should be called while holding a
138 // lock. It will try to first allocate lock-free out of the active
139 // region or, if it's unable to, it will try to replace the active
140 // alloc region with a new one. We require that the caller takes the
141 // appropriate lock before calling this so that it is easier to make
142 // it conform to its locking protocol.
143 inline HeapWord* attempt_allocation_locked(size_t word_size,
144 bool bot_updates);
145
146 // Should be called to allocate a new region even if the max of this
147 // type of regions has been reached. Should only be called if other
148 // allocation attempts have failed and we are not holding a valid
149 // active region.
150 inline HeapWord* attempt_allocation_force(size_t word_size,
151 bool bot_updates);
152
153 // Should be called before we start using this object.
154 void init();
155
156 // Should be called when we want to release the active region which
157 // is returned after it's been retired.
158 HeapRegion* release();
159
160 #if G1_ALLOC_REGION_TRACING
161 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);
162 #else // G1_ALLOC_REGION_TRACING
163 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }
164 #endif // G1_ALLOC_REGION_TRACING
165 };
166
167 class ar_ext_msg : public err_msg {
168 public:
169 ar_ext_msg(G1AllocRegion* alloc_region, const char *message) : err_msg("") {
170 alloc_region->fill_in_ext_msg(this, message);
171 }
172 };
173
174 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP

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