1 /*
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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).
14 *
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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 and 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* volatile _alloc_region;
59
60 // It keeps track of the distinct number of regions that are used
61 // for allocation in the active interval of this object, i.e.,
62 // between a call to init() and a call to release(). The count
63 // mostly includes regions that are freshly allocated, as well as
64 // the region that is re-used using the set() method. This count can
65 // be used in any heuristics that might want to bound how many
66 // distinct regions this object can used during an active interval.
67 uint _count;
68
69 // When we set up a new active region we save its used bytes in this
70 // field so that, when we retire it, we can calculate how much space
71 // we allocated in it.
72 size_t _used_bytes_before;
73
74 // When true, indicates that allocate calls should do BOT updates.
75 const bool _bot_updates;
76
77 // Useful for debugging and tracing.
78 const char* _name;
79
80 // A dummy region (i.e., it's been allocated specially for this
81 // purpose and it is not part of the heap) that is full (i.e., top()
82 // == end()). When we don't have a valid active region we make
83 // _alloc_region point to this. This allows us to skip checking
84 // whether the _alloc_region is NULL or not.
85 static HeapRegion* _dummy_region;
86
87 // Some of the methods below take a bot_updates parameter. Its value
88 // should be the same as the _bot_updates field. The idea is that
89 // the parameter will be a constant for a particular alloc region
90 // and, given that these methods will be hopefully inlined, the
91 // compiler should compile out the test.
92
93 // Perform a non-MT-safe allocation out of the given region.
94 static inline HeapWord* allocate(HeapRegion* alloc_region,
95 size_t word_size,
96 bool bot_updates);
97
98 // Perform a MT-safe allocation out of the given region.
99 static inline HeapWord* par_allocate(HeapRegion* alloc_region,
100 size_t word_size,
101 bool bot_updates);
102
103 // Ensure that the region passed as a parameter has been filled up
104 // so that noone else can allocate out of it any more.
105 static void fill_up_remaining_space(HeapRegion* alloc_region,
106 bool bot_updates);
107
108 // Retire the active allocating region. If fill_up is true then make
109 // sure that the region is full before we retire it so that noone
110 // else can allocate out of it.
111 void retire(bool fill_up);
112
113 // Allocate a new active region and use it to perform a word_size
114 // allocation. The force parameter will be passed on to
115 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
116 // to allocate a new region even if the max has been reached.
117 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
118
119 void fill_in_ext_msg(ar_ext_msg* msg, const char* message);
120
121 protected:
122 // For convenience as subclasses use it.
123 static G1CollectedHeap* _g1h;
124
125 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
126 virtual void retire_region(HeapRegion* alloc_region,
127 size_t allocated_bytes) = 0;
128
129 G1AllocRegion(const char* name, bool bot_updates);
130
131 public:
132 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
133
134 HeapRegion* get() const {
135 HeapRegion * hr = _alloc_region;
136 // Make sure that the dummy region does not escape this class.
137 return (hr == _dummy_region) ? NULL : hr;
138 }
139
140 uint count() { return _count; }
141
142 // The following two are the building blocks for the allocation method.
143
144 // First-level allocation: Should be called without holding a
145 // lock. It will try to allocate lock-free out of the active region,
146 // or return NULL if it was unable to.
147 inline HeapWord* attempt_allocation(size_t word_size, bool bot_updates);
148
149 // Second-level allocation: Should be called while holding a
150 // lock. It will try to first allocate lock-free out of the active
151 // region or, if it's unable to, it will try to replace the active
152 // alloc region with a new one. We require that the caller takes the
153 // appropriate lock before calling this so that it is easier to make
154 // it conform to its locking protocol.
155 inline HeapWord* attempt_allocation_locked(size_t word_size,
156 bool bot_updates);
157
158 // Should be called to allocate a new region even if the max of this
159 // type of regions has been reached. Should only be called if other
160 // allocation attempts have failed and we are not holding a valid
161 // active region.
162 inline HeapWord* attempt_allocation_force(size_t word_size,
163 bool bot_updates);
164
165 // Should be called before we start using this object.
166 void init();
167
168 // This can be used to set the active region to a specific
169 // region. (Use Example: we try to retain the last old GC alloc
170 // region that we've used during a GC and we can use set() to
171 // re-instate it at the beginning of the next GC.)
172 void set(HeapRegion* alloc_region);
173
174 // Should be called when we want to release the active region which
175 // is returned after it's been retired.
176 HeapRegion* release();
177
178 #if G1_ALLOC_REGION_TRACING
179 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);
180 #else // G1_ALLOC_REGION_TRACING
181 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }
182 #endif // G1_ALLOC_REGION_TRACING
183 };
184
185 class ar_ext_msg : public err_msg {
186 public:
187 ar_ext_msg(G1AllocRegion* alloc_region, const char *message) : err_msg("") {
188 alloc_region->fill_in_ext_msg(this, message);
189 }
190 };
191
192 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP