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 {
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 // It keeps track of the distinct number of regions that are used
57 // for allocation in the active interval of this object, i.e.,
58 // between a call to init() and a call to release(). The count
59 // mostly includes regions that are freshly allocated, as well as
60 // the region that is re-used using the set() method. This count can
61 // be used in any heuristics that might want to bound how many
62 // distinct regions this object can used during an active interval.
63 uint _count;
64
65 // When we set up a new active region we save its used bytes in this
66 // field so that, when we retire it, we can calculate how much space
67 // we allocated in it.
68 size_t _used_bytes_before;
69
70 // When true, indicates that allocate calls should do BOT updates.
71 const bool _bot_updates;
72
73 // Useful for debugging and tracing.
74 const char* _name;
75
76 // A dummy region (i.e., it's been allocated specially for this
77 // purpose and it is not part of the heap) that is full (i.e., top()
78 // == end()). When we don't have a valid active region we make
79 // _alloc_region point to this. This allows us to skip checking
80 // whether the _alloc_region is NULL or not.
81 static HeapRegion* _dummy_region;
82
83 // Perform a non-MT-safe allocation out of the given region.
84 inline HeapWord* allocate(HeapRegion* alloc_region,
85 size_t word_size);
86
87 // Perform a MT-safe allocation out of the given region.
88 inline HeapWord* par_allocate(HeapRegion* alloc_region,
89 size_t word_size);
90 // Perform a MT-safe allocation out of the given region, with the given
91 // minimum and desired size. Returns the actual size allocated (between
92 // minimum and desired size) in actual_word_size if the allocation has been
93 // successful.
94 inline HeapWord* par_allocate(HeapRegion* alloc_region,
95 size_t min_word_size,
96 size_t desired_word_size,
97 size_t* actual_word_size);
98
99 // Ensure that the region passed as a parameter has been filled up
100 // so that noone else can allocate out of it any more.
101 // Returns the number of bytes that have been wasted by filled up
102 // the space.
103 size_t fill_up_remaining_space(HeapRegion* alloc_region);
104
105 // After a region is allocated by alloc_new_region, this
106 // method is used to set it as the active alloc_region
107 void update_alloc_region(HeapRegion* alloc_region);
108
109 // Allocate a new active region and use it to perform a word_size
110 // allocation. The force parameter will be passed on to
111 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
112 // to allocate a new region even if the max has been reached.
113 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
114
115 protected:
116 // Retire the active allocating region. If fill_up is true then make
117 // sure that the region is full before we retire it so that no one
118 // else can allocate out of it.
119 // Returns the number of bytes that have been filled up during retire.
120 virtual size_t retire(bool fill_up);
121
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);
148 // Perform an allocation out of the current allocation region, with the given
149 // minimum and desired size. Returns the actual size allocated (between
150 // minimum and desired size) in actual_word_size if the allocation has been
151 // successful.
152 // Should be called without holding a lock. It will try to allocate lock-free
153 // out of the active region, or return NULL if it was unable to.
154 inline HeapWord* attempt_allocation(size_t min_word_size,
155 size_t desired_word_size,
156 size_t* actual_word_size);
157
158 // Second-level allocation: Should be called while holding a
159 // lock. It will try to first allocate lock-free out of the active
160 // region or, if it's unable to, it will try to replace the active
161 // alloc region with a new one. We require that the caller takes the
162 // appropriate lock before calling this so that it is easier to make
163 // it conform to its locking protocol.
164 inline HeapWord* attempt_allocation_locked(size_t word_size);
165 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
166 // of minimum word size of the block in min_word_size, and the maximum word
167 // size of the allocation in desired_word_size. The actual size of the block is
168 // returned in actual_word_size.
169 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
170 size_t desired_word_size,
171 size_t* actual_word_size);
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
179 // Should be called before we start using this object.
180 void init();
181
182 // This can be used to set the active region to a specific
183 // region. (Use Example: we try to retain the last old GC alloc
184 // region that we've used during a GC and we can use set() to
185 // re-instate it at the beginning of the next GC.)
186 void set(HeapRegion* alloc_region);
187
188 // Should be called when we want to release the active region which
189 // is returned after it's been retired.
190 virtual HeapRegion* release();
191
192 void trace(const char* str,
193 size_t min_word_size = 0,
194 size_t desired_word_size = 0,
195 size_t actual_word_size = 0,
196 HeapWord* result = NULL) PRODUCT_RETURN;
197 };
198
199 class MutatorAllocRegion : public G1AllocRegion {
200 protected:
201 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
202 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
203 public:
204 MutatorAllocRegion()
205 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
206 };
207
208 // Common base class for allocation regions used during GC.
209 class G1GCAllocRegion : public G1AllocRegion {
210 protected:
211 G1EvacStats* _stats;
212 InCSetState::in_cset_state_t _purpose;
213
214 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
215 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
216
217 virtual size_t retire(bool fill_up);
218
219 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, InCSetState::in_cset_state_t purpose)
220 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
221 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
222 }
223 };
224
225 class SurvivorGCAllocRegion : public G1GCAllocRegion {
226 public:
227 SurvivorGCAllocRegion(G1EvacStats* stats)
228 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, InCSetState::Young) { }
229 };
230
231 class OldGCAllocRegion : public G1GCAllocRegion {
232 public:
233 OldGCAllocRegion(G1EvacStats* stats)
234 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, InCSetState::Old) { }
235
236 // This specialization of release() makes sure that the last card that has
237 // been allocated into has been completely filled by a dummy object. This
238 // avoids races when remembered set scanning wants to update the BOT of the
239 // last card in the retained old gc alloc region, and allocation threads
240 // allocating into that card at the same time.
241 virtual HeapRegion* release();
242 };
243
244 #endif // SHARE_VM_GC_G1_G1ALLOCREGION_HPP