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.
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5 * This code is free software; you can redistribute it and/or modify it
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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 // A class that holds a region that is active in satisfying allocation
35 // requests, potentially issued in parallel. When the active region is
36 // full it will be retired and replaced with a new one. The
37 // implementation assumes that fast-path allocations will be lock-free
38 // and a lock will need to be taken when the active region needs to be
39 // replaced.
40
41 class G1AllocRegion VALUE_OBJ_CLASS_SPEC {
42
43 private:
44 // The active allocating region we are currently allocating out
45 // of. The invariant is that if this object is initialized (i.e.,
46 // init() has been called and release() has not) then _alloc_region
47 // is either an active allocating region or the dummy region (i.e.,
48 // it can never be NULL) and this object can be used to satisfy
49 // allocation requests. If this object is not initialized
50 // (i.e. init() has not been called or release() has been called)
51 // then _alloc_region is NULL and this object should not be used to
52 // satisfy allocation requests (it was done this way to force the
53 // correct use of init() and release()).
54 HeapRegion* volatile _alloc_region;
55
56 // Allocation context associated with this alloc region.
57 AllocationContext_t _allocation_context;
58
59 // It keeps track of the distinct number of regions that are used
60 // for allocation in the active interval of this object, i.e.,
61 // between a call to init() and a call to release(). The count
62 // mostly includes regions that are freshly allocated, as well as
63 // the region that is re-used using the set() method. This count can
64 // be used in any heuristics that might want to bound how many
65 // distinct regions this object can used during an active interval.
66 uint _count;
67
68 // When we set up a new active region we save its used bytes in this
69 // field so that, when we retire it, we can calculate how much space
70 // we allocated in it.
71 size_t _used_bytes_before;
72
73 // When true, indicates that allocate calls should do BOT updates.
74 const bool _bot_updates;
75
76 // Useful for debugging and tracing.
77 const char* _name;
78
79 // A dummy region (i.e., it's been allocated specially for this
80 // purpose and it is not part of the heap) that is full (i.e., top()
81 // == end()). When we don't have a valid active region we make
82 // _alloc_region point to this. This allows us to skip checking
83 // whether the _alloc_region is NULL or not.
84 static HeapRegion* _dummy_region;
85
86 // Some of the methods below take a bot_updates parameter. Its value
87 // should be the same as the _bot_updates field. The idea is that
88 // the parameter will be a constant for a particular alloc region
89 // and, given that these methods will be hopefully inlined, the
90 // compiler should compile out the test.
91
92 // Perform a non-MT-safe allocation out of the given region.
93 static inline HeapWord* allocate(HeapRegion* alloc_region,
94 size_t word_size,
95 bool bot_updates);
96
97 // Perform a MT-safe allocation out of the given region.
98 static inline HeapWord* par_allocate(HeapRegion* alloc_region,
99 size_t word_size,
100 bool bot_updates);
101 // Perform a MT-safe allocation out of the given region, with the given
102 // minimum and desired size. Returns the actual size allocated (between
103 // minimum and desired size) in actual_word_size if the allocation has been
104 // successful.
105 static inline HeapWord* par_allocate(HeapRegion* alloc_region,
106 size_t min_word_size,
107 size_t desired_word_size,
108 size_t* actual_word_size,
109 bool bot_updates);
110
111 // Ensure that the region passed as a parameter has been filled up
112 // so that noone else can allocate out of it any more.
113 // Returns the number of bytes that have been wasted by filled up
114 // the space.
115 static size_t fill_up_remaining_space(HeapRegion* alloc_region,
116 bool bot_updates);
117
118 // After a region is allocated by alloc_new_region, this
119 // method is used to set it as the active alloc_region
120 void update_alloc_region(HeapRegion* alloc_region);
121
122 // Allocate a new active region and use it to perform a word_size
123 // allocation. The force parameter will be passed on to
124 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
125 // to allocate a new region even if the max has been reached.
126 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
127
128 protected:
129 // Retire the active allocating region. If fill_up is true then make
130 // sure that the region is full before we retire it so that no one
131 // else can allocate out of it.
132 // Returns the number of bytes that have been filled up during retire.
133 virtual size_t retire(bool fill_up);
134
135 // For convenience as subclasses use it.
136 static G1CollectedHeap* _g1h;
137
138 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
139 virtual void retire_region(HeapRegion* alloc_region,
140 size_t allocated_bytes) = 0;
141
142 G1AllocRegion(const char* name, bool bot_updates);
143
144 public:
145 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
146
147 HeapRegion* get() const {
148 HeapRegion * hr = _alloc_region;
149 // Make sure that the dummy region does not escape this class.
150 return (hr == _dummy_region) ? NULL : hr;
151 }
152
153 void set_allocation_context(AllocationContext_t context) { _allocation_context = context; }
154 AllocationContext_t allocation_context() { return _allocation_context; }
155
156 uint count() { return _count; }
157
158 // The following two are the building blocks for the allocation method.
159
160 // First-level allocation: Should be called without holding a
161 // lock. It will try to allocate lock-free out of the active region,
162 // or return NULL if it was unable to.
163 inline HeapWord* attempt_allocation(size_t word_size,
164 bool bot_updates);
165 // Perform an allocation out of the current allocation region, with the given
166 // minimum and desired size. Returns the actual size allocated (between
167 // minimum and desired size) in actual_word_size if the allocation has been
168 // successful.
169 // Should be called without holding a lock. It will try to allocate lock-free
170 // out of the active region, or return NULL if it was unable to.
171 inline HeapWord* attempt_allocation(size_t min_word_size,
172 size_t desired_word_size,
173 size_t* actual_word_size,
174 bool bot_updates);
175
176 // Second-level allocation: Should be called while holding a
177 // lock. It will try to first allocate lock-free out of the active
178 // region or, if it's unable to, it will try to replace the active
179 // alloc region with a new one. We require that the caller takes the
180 // appropriate lock before calling this so that it is easier to make
181 // it conform to its locking protocol.
182 inline HeapWord* attempt_allocation_locked(size_t word_size,
183 bool bot_updates);
184 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
185 // of minimum word size of the block in min_word_size, and the maximum word
186 // size of the allocation in desired_word_size. The actual size of the block is
187 // returned in actual_word_size.
188 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
189 size_t desired_word_size,
190 size_t* actual_word_size,
191 bool bot_updates);
192
193 // Should be called to allocate a new region even if the max of this
194 // type of regions has been reached. Should only be called if other
195 // allocation attempts have failed and we are not holding a valid
196 // active region.
197 inline HeapWord* attempt_allocation_force(size_t word_size,
198 bool bot_updates);
199
200 // Should be called before we start using this object.
201 void init();
202
203 // This can be used to set the active region to a specific
204 // region. (Use Example: we try to retain the last old GC alloc
205 // region that we've used during a GC and we can use set() to
206 // re-instate it at the beginning of the next GC.)
207 void set(HeapRegion* alloc_region);
208
209 // Should be called when we want to release the active region which
210 // is returned after it's been retired.
211 virtual HeapRegion* release();
212
213 #ifndef PRODUCT
214 void trace(const char* str,
215 size_t min_word_size = 0,
216 size_t desired_word_size = 0,
217 size_t actual_word_size = 0,
218 HeapWord* result = NULL);
219 #else // PRODUCT
220 void trace(const char* str,
221 size_t min_word_size = 0,
222 size_t desired_word_size = 0,
223 size_t actual_word_size = 0,
224 HeapWord* result = NULL) { }
225 #endif // PRODUCT
226 };
227
228 class MutatorAllocRegion : public G1AllocRegion {
229 protected:
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 public:
233 MutatorAllocRegion()
234 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
235 };
236
237 // Common base class for allocation regions used during GC.
238 class G1GCAllocRegion : public G1AllocRegion {
239 protected:
240 G1EvacStats* _stats;
241 InCSetState::in_cset_state_t _purpose;
242
243 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
244 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
245
246 virtual size_t retire(bool fill_up);
247 public:
248 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, InCSetState::in_cset_state_t purpose)
249 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
250 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
251 }
252 };
253
254 class SurvivorGCAllocRegion : public G1GCAllocRegion {
255 public:
256 SurvivorGCAllocRegion(G1EvacStats* stats)
257 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, InCSetState::Young) { }
258 };
259
260 class OldGCAllocRegion : public G1GCAllocRegion {
261 public:
262 OldGCAllocRegion(G1EvacStats* stats)
263 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, InCSetState::Old) { }
264
265 // This specialization of release() makes sure that the last card that has
266 // been allocated into has been completely filled by a dummy object. This
267 // avoids races when remembered set scanning wants to update the BOT of the
268 // last card in the retained old gc alloc region, and allocation threads
269 // allocating into that card at the same time.
270 virtual HeapRegion* release();
271 };
272
273 #endif // SHARE_VM_GC_G1_G1ALLOCREGION_HPP