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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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 // Perform a non-MT-safe allocation out of the given region.
87 inline HeapWord* allocate(HeapRegion* alloc_region,
88 size_t word_size);
89
90 // Perform a MT-safe allocation out of the given region.
91 inline HeapWord* par_allocate(HeapRegion* alloc_region,
92 size_t word_size);
93 // Perform a MT-safe allocation out of the given region, with the given
94 // minimum and desired size. Returns the actual size allocated (between
95 // minimum and desired size) in actual_word_size if the allocation has been
96 // successful.
97 inline HeapWord* par_allocate(HeapRegion* alloc_region,
98 size_t min_word_size,
99 size_t desired_word_size,
100 size_t* actual_word_size);
101
102 // Ensure that the region passed as a parameter has been filled up
103 // so that noone else can allocate out of it any more.
104 // Returns the number of bytes that have been wasted by filled up
105 // the space.
106 size_t fill_up_remaining_space(HeapRegion* alloc_region);
107
108 // After a region is allocated by alloc_new_region, this
109 // method is used to set it as the active alloc_region
110 void update_alloc_region(HeapRegion* alloc_region);
111
112 // Allocate a new active region and use it to perform a word_size
113 // allocation. The force parameter will be passed on to
114 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
115 // to allocate a new region even if the max has been reached.
116 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
117
118 protected:
119 // Retire the active allocating region. If fill_up is true then make
120 // sure that the region is full before we retire it so that no one
121 // else can allocate out of it.
122 // Returns the number of bytes that have been filled up during retire.
123 virtual size_t retire(bool fill_up);
124
125 // For convenience as subclasses use it.
126 static G1CollectedHeap* _g1h;
127
128 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
129 virtual void retire_region(HeapRegion* alloc_region,
130 size_t allocated_bytes) = 0;
131
132 G1AllocRegion(const char* name, bool bot_updates);
133
134 public:
135 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
136
137 HeapRegion* get() const {
138 HeapRegion * hr = _alloc_region;
139 // Make sure that the dummy region does not escape this class.
140 return (hr == _dummy_region) ? NULL : hr;
141 }
142
143 void set_allocation_context(AllocationContext_t context) { _allocation_context = context; }
144 AllocationContext_t allocation_context() { return _allocation_context; }
145
146 uint count() { return _count; }
147
148 // The following two are the building blocks for the allocation method.
149
150 // First-level allocation: Should be called without holding a
151 // lock. It will try to allocate lock-free out of the active region,
152 // or return NULL if it was unable to.
153 inline HeapWord* attempt_allocation(size_t word_size);
154 // Perform an allocation out of the current allocation region, with the given
155 // minimum and desired size. Returns the actual size allocated (between
156 // minimum and desired size) in actual_word_size if the allocation has been
157 // successful.
158 // Should be called without holding a lock. It will try to allocate lock-free
159 // out of the active region, or return NULL if it was unable to.
160 inline HeapWord* attempt_allocation(size_t min_word_size,
161 size_t desired_word_size,
162 size_t* actual_word_size);
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 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
172 // of minimum word size of the block in min_word_size, and the maximum word
173 // size of the allocation in desired_word_size. The actual size of the block is
174 // returned in actual_word_size.
175 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
176 size_t desired_word_size,
177 size_t* actual_word_size);
178
179 // Should be called to allocate a new region even if the max of this
180 // type of regions has been reached. Should only be called if other
181 // allocation attempts have failed and we are not holding a valid
182 // active region.
183 inline HeapWord* attempt_allocation_force(size_t word_size);
184
185 // Should be called before we start using this object.
186 void init();
187
188 // This can be used to set the active region to a specific
189 // region. (Use Example: we try to retain the last old GC alloc
190 // region that we've used during a GC and we can use set() to
191 // re-instate it at the beginning of the next GC.)
192 void set(HeapRegion* alloc_region);
193
194 // Should be called when we want to release the active region which
195 // is returned after it's been retired.
196 virtual HeapRegion* release();
197
198 void trace(const char* str,
199 size_t min_word_size = 0,
200 size_t desired_word_size = 0,
201 size_t actual_word_size = 0,
202 HeapWord* result = NULL) PRODUCT_RETURN;
203 };
204
205 class MutatorAllocRegion : public G1AllocRegion {
206 protected:
207 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
208 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
209 public:
210 MutatorAllocRegion()
211 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
212 };
213
214 // Common base class for allocation regions used during GC.
215 class G1GCAllocRegion : public G1AllocRegion {
216 protected:
217 G1EvacStats* _stats;
218 InCSetState::in_cset_state_t _purpose;
219
220 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
221 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
222
223 virtual size_t retire(bool fill_up);
224
225 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, InCSetState::in_cset_state_t purpose)
226 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
227 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
228 }
229 };
230
231 class SurvivorGCAllocRegion : public G1GCAllocRegion {
232 public:
233 SurvivorGCAllocRegion(G1EvacStats* stats)
234 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, InCSetState::Young) { }
235 };
236
237 class OldGCAllocRegion : public G1GCAllocRegion {
238 public:
239 OldGCAllocRegion(G1EvacStats* stats)
240 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, InCSetState::Old) { }
241
242 // This specialization of release() makes sure that the last card that has
243 // been allocated into has been completely filled by a dummy object. This
244 // avoids races when remembered set scanning wants to update the BOT of the
245 // last card in the retained old gc alloc region, and allocation threads
246 // allocating into that card at the same time.
247 virtual HeapRegion* release();
248 };
249
250 #endif // SHARE_VM_GC_G1_G1ALLOCREGION_HPP