1 /*
2 * Copyright (c) 2011, 2015, 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.
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1ALLOCREGION_HPP
26 #define SHARE_VM_GC_G1_G1ALLOCREGION_HPP
27
28 #include "gc/g1/heapRegion.hpp"
29 #include "gc/g1/g1EvacStats.hpp"
30 #include "gc/g1/g1InCSetState.hpp"
31
32 class G1CollectedHeap;
33
34 // 0 -> no tracing, 1 -> basic tracing, 2 -> basic + allocation tracing
35 #define G1_ALLOC_REGION_TRACING 0
36
37 class ar_ext_msg;
38
39 // A class that holds a region that is active in satisfying allocation
40 // requests, potentially issued in parallel. When the active region is
41 // full it will be retired and replaced with a new one. The
42 // implementation assumes that fast-path allocations will be lock-free
43 // and a lock will need to be taken when the active region needs to be
44 // replaced.
45
46 class G1AllocRegion VALUE_OBJ_CLASS_SPEC {
47 friend class ar_ext_msg;
48
49 private:
50 // The active allocating region we are currently allocating out
51 // of. The invariant is that if this object is initialized (i.e.,
52 // init() has been called and release() has not) then _alloc_region
53 // is either an active allocating region or the dummy region (i.e.,
54 // it can never be NULL) and this object can be used to satisfy
55 // allocation requests. If this object is not initialized
56 // (i.e. init() has not been called or release() has been called)
57 // then _alloc_region is NULL and this object should not be used to
58 // satisfy allocation requests (it was done this way to force the
59 // correct use of init() and release()).
60 HeapRegion* volatile _alloc_region;
61
62 // Allocation context associated with this alloc region.
63 AllocationContext_t _allocation_context;
64
65 // It keeps track of the distinct number of regions that are used
66 // for allocation in the active interval of this object, i.e.,
67 // between a call to init() and a call to release(). The count
68 // mostly includes regions that are freshly allocated, as well as
69 // the region that is re-used using the set() method. This count can
70 // be used in any heuristics that might want to bound how many
71 // distinct regions this object can used during an active interval.
72 uint _count;
73
74 // When we set up a new active region we save its used bytes in this
75 // field so that, when we retire it, we can calculate how much space
76 // we allocated in it.
77 size_t _used_bytes_before;
78
79 // When true, indicates that allocate calls should do BOT updates.
80 const bool _bot_updates;
81
82 // Useful for debugging and tracing.
83 const char* _name;
84
85 // A dummy region (i.e., it's been allocated specially for this
86 // purpose and it is not part of the heap) that is full (i.e., top()
87 // == end()). When we don't have a valid active region we make
88 // _alloc_region point to this. This allows us to skip checking
89 // whether the _alloc_region is NULL or not.
90 static HeapRegion* _dummy_region;
91
92 // Some of the methods below take a bot_updates parameter. Its value
93 // should be the same as the _bot_updates field. The idea is that
94 // the parameter will be a constant for a particular alloc region
95 // and, given that these methods will be hopefully inlined, the
96 // compiler should compile out the test.
97
98 // Perform a non-MT-safe allocation out of the given region.
99 static inline HeapWord* allocate(HeapRegion* alloc_region,
100 size_t word_size,
101 bool bot_updates);
102
103 // Perform a MT-safe allocation out of the given region.
104 static inline HeapWord* par_allocate(HeapRegion* alloc_region,
105 size_t word_size,
106 bool bot_updates);
107 static inline HeapWord* par_allocate(HeapRegion* alloc_region,
108 size_t min_word_size,
109 size_t* actual_word_size,
110 bool bot_updates);
111
112 // Ensure that the region passed as a parameter has been filled up
113 // so that noone else can allocate out of it any more.
114 // Returns the number of bytes that have been wasted by filled up
115 // the space.
116 static size_t fill_up_remaining_space(HeapRegion* alloc_region,
117 bool bot_updates);
118
119 // After a region is allocated by alloc_new_region, this
120 // method is used to set it as the active alloc_region
121 void update_alloc_region(HeapRegion* alloc_region);
122
123 // Allocate a new active region and use it to perform a word_size
124 // allocation. The force parameter will be passed on to
125 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
126 // to allocate a new region even if the max has been reached.
127 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
128
129 void fill_in_ext_msg(ar_ext_msg* msg, const char* message);
130
131 protected:
132 // Retire the active allocating region. If fill_up is true then make
133 // sure that the region is full before we retire it so that no one
134 // else can allocate out of it.
135 // Returns the number of bytes that have been filled up during retire.
136 virtual size_t retire(bool fill_up);
137
138 // For convenience as subclasses use it.
139 static G1CollectedHeap* _g1h;
140
141 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
142 virtual void retire_region(HeapRegion* alloc_region,
143 size_t allocated_bytes) = 0;
144
145 G1AllocRegion(const char* name, bool bot_updates);
146
147 public:
148 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
149
150 HeapRegion* get() const {
151 HeapRegion * hr = _alloc_region;
152 // Make sure that the dummy region does not escape this class.
153 return (hr == _dummy_region) ? NULL : hr;
154 }
155
156 void set_allocation_context(AllocationContext_t context) { _allocation_context = context; }
157 AllocationContext_t allocation_context() { return _allocation_context; }
158
159 uint count() { return _count; }
160
161 // The following two are the building blocks for the allocation method.
162
163 // First-level allocation: Should be called without holding a
164 // lock. It will try to allocate lock-free out of the active region,
165 // or return NULL if it was unable to.
166 inline HeapWord* attempt_allocation(size_t word_size,
167 bool bot_updates);
168 inline HeapWord* attempt_allocation(size_t min_word_size,
169 size_t* word_size,
170 bool bot_updates);
171
172 // Second-level allocation: Should be called while holding a
173 // lock. It will try to first allocate lock-free out of the active
174 // region or, if it's unable to, it will try to replace the active
175 // alloc region with a new one. We require that the caller takes the
176 // appropriate lock before calling this so that it is easier to make
177 // it conform to its locking protocol.
178 inline HeapWord* attempt_allocation_locked(size_t word_size,
179 bool bot_updates);
180 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
181 // of minimum word size of the block in min_word_size, and the maximum word
182 // size of the allocation in word_size. The actual size of the block is returned
183 // in word_size.
184 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
185 size_t* word_size,
186 bool bot_updates);
187
188 // Should be called to allocate a new region even if the max of this
189 // type of regions has been reached. Should only be called if other
190 // allocation attempts have failed and we are not holding a valid
191 // active region.
192 inline HeapWord* attempt_allocation_force(size_t word_size,
193 bool bot_updates);
194
195 // Should be called before we start using this object.
196 void init();
197
198 // This can be used to set the active region to a specific
199 // region. (Use Example: we try to retain the last old GC alloc
200 // region that we've used during a GC and we can use set() to
201 // re-instate it at the beginning of the next GC.)
202 void set(HeapRegion* alloc_region);
203
204 // Should be called when we want to release the active region which
205 // is returned after it's been retired.
206 virtual HeapRegion* release();
207
208 #if G1_ALLOC_REGION_TRACING
209 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);
210 #else // G1_ALLOC_REGION_TRACING
211 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }
212 #endif // G1_ALLOC_REGION_TRACING
213 };
214
215 class MutatorAllocRegion : public G1AllocRegion {
216 protected:
217 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
218 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
219 public:
220 MutatorAllocRegion()
221 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
222 };
223
224 // Common base class for allocation regions used during GC.
225 class G1GCAllocRegion : public G1AllocRegion {
226 protected:
227 G1EvacStats* _stats;
228 InCSetState::in_cset_state_t _purpose;
229
230 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
231 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
232
233 virtual size_t retire(bool fill_up);
234 public:
235 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, InCSetState::in_cset_state_t purpose)
236 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
237 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
238 }
239 };
240
241 class SurvivorGCAllocRegion : public G1GCAllocRegion {
242 public:
243 SurvivorGCAllocRegion(G1EvacStats* stats)
244 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, InCSetState::Young) { }
245 };
246
247 class OldGCAllocRegion : public G1GCAllocRegion {
248 public:
249 OldGCAllocRegion(G1EvacStats* stats)
250 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, InCSetState::Old) { }
251
252 // This specialization of release() makes sure that the last card that has
253 // been allocated into has been completely filled by a dummy object. This
254 // avoids races when remembered set scanning wants to update the BOT of the
255 // last card in the retained old gc alloc region, and allocation threads
256 // allocating into that card at the same time.
257 virtual HeapRegion* release();
258 };
259
260 class ar_ext_msg : public err_msg {
261 public:
262 ar_ext_msg(G1AllocRegion* alloc_region, const char *message) : err_msg("%s", "") {
263 alloc_region->fill_in_ext_msg(this, message);
264 }
265 };
266
267 #endif // SHARE_VM_GC_G1_G1ALLOCREGION_HPP