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
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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
108 // Ensure that the region passed as a parameter has been filled up
109 // so that noone else can allocate out of it any more.
110 // Returns the number of bytes that have been wasted by filled up
111 // the space.
112 static size_t fill_up_remaining_space(HeapRegion* alloc_region,
113 bool bot_updates);
114
115 // After a region is allocated by alloc_new_region, this
116 // method is used to set it as the active alloc_region
117 void update_alloc_region(HeapRegion* alloc_region);
118
119 // Allocate a new active region and use it to perform a word_size
120 // allocation. The force parameter will be passed on to
121 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
122 // to allocate a new region even if the max has been reached.
123 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
124
125 void fill_in_ext_msg(ar_ext_msg* msg, const char* message);
126
127 protected:
128 // Retire the active allocating region. If fill_up is true then make
129 // sure that the region is full before we retire it so that no one
130 // else can allocate out of it.
131 // Returns the number of bytes that have been filled up during retire.
132 virtual size_t retire(bool fill_up);
133
134 // For convenience as subclasses use it.
135 static G1CollectedHeap* _g1h;
136
137 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
138 virtual void retire_region(HeapRegion* alloc_region,
139 size_t allocated_bytes) = 0;
140
141 G1AllocRegion(const char* name, bool bot_updates);
142
143 public:
144 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
145
146 HeapRegion* get() const {
147 HeapRegion * hr = _alloc_region;
148 // Make sure that the dummy region does not escape this class.
149 return (hr == _dummy_region) ? NULL : hr;
150 }
151
152 void set_allocation_context(AllocationContext_t context) { _allocation_context = context; }
153 AllocationContext_t allocation_context() { return _allocation_context; }
154
155 uint count() { return _count; }
156
157 // The following two are the building blocks for the allocation method.
158
159 // First-level allocation: Should be called without holding a
160 // lock. It will try to allocate lock-free out of the active region,
161 // or return NULL if it was unable to.
162 inline HeapWord* attempt_allocation(size_t word_size, bool bot_updates);
163
164 // Second-level allocation: Should be called while holding a
165 // lock. It will try to first allocate lock-free out of the active
166 // region or, if it's unable to, it will try to replace the active
167 // alloc region with a new one. We require that the caller takes the
168 // appropriate lock before calling this so that it is easier to make
169 // it conform to its locking protocol.
170 inline HeapWord* attempt_allocation_locked(size_t word_size,
171 bool bot_updates);
172
173 // Should be called to allocate a new region even if the max of this
174 // type of regions has been reached. Should only be called if other
175 // allocation attempts have failed and we are not holding a valid
176 // active region.
177 inline HeapWord* attempt_allocation_force(size_t word_size,
178 bool bot_updates);
179
180 // Should be called before we start using this object.
181 void init();
182
183 // This can be used to set the active region to a specific
184 // region. (Use Example: we try to retain the last old GC alloc
185 // region that we've used during a GC and we can use set() to
186 // re-instate it at the beginning of the next GC.)
187 void set(HeapRegion* alloc_region);
188
189 // Should be called when we want to release the active region which
190 // is returned after it's been retired.
191 virtual HeapRegion* release();
192
193 #if G1_ALLOC_REGION_TRACING
194 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);
195 #else // G1_ALLOC_REGION_TRACING
196 void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }
197 #endif // G1_ALLOC_REGION_TRACING
198 };
199
200 class MutatorAllocRegion : public G1AllocRegion {
201 protected:
202 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
203 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
204 public:
205 MutatorAllocRegion()
206 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
207 };
208
209 // Common base class for allocation regions used during GC.
210 class G1GCAllocRegion : public G1AllocRegion {
211 protected:
212 G1EvacStats* _stats;
213 InCSetState::in_cset_state_t _purpose;
214
215 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
216 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
217
218 virtual size_t retire(bool fill_up);
219 public:
220 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, InCSetState::in_cset_state_t purpose)
221 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
222 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
223 }
224 };
225
226 class SurvivorGCAllocRegion : public G1GCAllocRegion {
227 public:
228 SurvivorGCAllocRegion(G1EvacStats* stats)
229 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, InCSetState::Young) { }
230 };
231
232 class OldGCAllocRegion : public G1GCAllocRegion {
233 public:
234 OldGCAllocRegion(G1EvacStats* stats)
235 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, InCSetState::Old) { }
236
237 // This specialization of release() makes sure that the last card that has
238 // been allocated into has been completely filled by a dummy object. This
239 // avoids races when remembered set scanning wants to update the BOT of the
240 // last card in the retained old gc alloc region, and allocation threads
241 // allocating into that card at the same time.
242 virtual HeapRegion* release();
243 };
244
245 class ar_ext_msg : public err_msg {
246 public:
247 ar_ext_msg(G1AllocRegion* alloc_region, const char *message) : err_msg("%s", "") {
248 alloc_region->fill_in_ext_msg(this, message);
249 }
250 };
251
252 #endif // SHARE_VM_GC_G1_G1ALLOCREGION_HPP