1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_GC_G1_G1ALLOCREGION_HPP
26 #define SHARE_GC_G1_G1ALLOCREGION_HPP
27
28 #include "gc/g1/heapRegion.hpp"
29 #include "gc/g1/g1EvacStats.hpp"
30 #include "gc/g1/g1HeapRegionAttr.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 // After a region is allocated by alloc_new_region, this
84 // method is used to set it as the active alloc_region
85 void update_alloc_region(HeapRegion* alloc_region);
86
87 // Allocate a new active region and use it to perform a word_size
88 // allocation. The force parameter will be passed on to
89 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
90 // to allocate a new region even if the max has been reached.
91 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
92
93 protected:
94 // Reset the alloc region to point a the dummy region.
95 void reset_alloc_region();
96
97 // Perform a non-MT-safe allocation out of the given region.
98 inline HeapWord* allocate(HeapRegion* alloc_region,
99 size_t word_size);
100
101 // Perform a MT-safe allocation out of the given region.
102 inline HeapWord* par_allocate(HeapRegion* alloc_region,
103 size_t word_size);
104 // Perform a MT-safe allocation out of the given region, with the given
105 // minimum and desired size. Returns the actual size allocated (between
106 // minimum and desired size) in actual_word_size if the allocation has been
107 // successful.
108 inline HeapWord* par_allocate(HeapRegion* alloc_region,
109 size_t min_word_size,
110 size_t desired_word_size,
111 size_t* actual_word_size);
112
113 // Ensure that the region passed as a parameter has been filled up
114 // so that noone else can allocate out of it any more.
115 // Returns the number of bytes that have been wasted by filled up
116 // the space.
117 size_t fill_up_remaining_space(HeapRegion* alloc_region);
118
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 size_t retire_internal(HeapRegion* alloc_region, bool fill_up);
126
127 // For convenience as subclasses use it.
128 static G1CollectedHeap* _g1h;
129
130 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
131 virtual void retire_region(HeapRegion* alloc_region,
132 size_t allocated_bytes) = 0;
133
134 G1AllocRegion(const char* name, bool bot_updates);
135
136 public:
137 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
138
139 HeapRegion* get() const {
140 HeapRegion * hr = _alloc_region;
141 // Make sure that the dummy region does not escape this class.
142 return (hr == _dummy_region) ? NULL : hr;
143 }
144
145 uint count() { return _count; }
146
147 // The following two are the building blocks for the allocation method.
148
149 // First-level allocation: Should be called without holding a
150 // lock. It will try to allocate lock-free out of the active region,
151 // or return NULL if it was unable to.
152 inline HeapWord* attempt_allocation(size_t word_size);
153 // Perform an allocation out of the current allocation region, with the given
154 // minimum and desired size. Returns the actual size allocated (between
155 // minimum and desired size) in actual_word_size if the allocation has been
156 // successful.
157 // Should be called without holding a lock. It will try to allocate lock-free
158 // out of the active region, or return NULL if it was unable to.
159 inline HeapWord* attempt_allocation(size_t min_word_size,
160 size_t desired_word_size,
161 size_t* actual_word_size);
162
163 // Second-level allocation: Should be called while holding a
164 // lock. It will try to first allocate lock-free out of the active
165 // region or, if it's unable to, it will try to replace the active
166 // alloc region with a new one. We require that the caller takes the
167 // appropriate lock before calling this so that it is easier to make
168 // it conform to its locking protocol.
169 inline HeapWord* attempt_allocation_locked(size_t word_size);
170 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
171 // of minimum word size of the block in min_word_size, and the maximum word
172 // size of the allocation in desired_word_size. The actual size of the block is
173 // returned in actual_word_size.
174 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
175 size_t desired_word_size,
176 size_t* actual_word_size);
177
178 // Should be called to allocate a new region even if the max of this
179 // type of regions has been reached. Should only be called if other
180 // allocation attempts have failed and we are not holding a valid
181 // active region.
182 inline HeapWord* attempt_allocation_force(size_t word_size);
183
184 // Should be called before we start using this object.
185 virtual void init();
186
187 // This can be used to set the active region to a specific
188 // region. (Use Example: we try to retain the last old GC alloc
189 // region that we've used during a GC and we can use set() to
190 // re-instate it at the beginning of the next GC.)
191 void set(HeapRegion* alloc_region);
192
193 // Should be called when we want to release the active region which
194 // is returned after it's been retired.
195 virtual HeapRegion* release();
196
197 void trace(const char* str,
198 size_t min_word_size = 0,
199 size_t desired_word_size = 0,
200 size_t actual_word_size = 0,
201 HeapWord* result = NULL) PRODUCT_RETURN;
202 };
203
204 class MutatorAllocRegion : public G1AllocRegion {
205 private:
206 // Keeps track of the total waste generated during the current
207 // mutator phase.
208 size_t _wasted_bytes;
209
210 // Retained allocation region. Used to lower the waste generated
211 // during mutation by having two active regions if the free space
212 // in a region about to be retired still could fit a TLAB.
213 HeapRegion* volatile _retained_alloc_region;
214
215 // Decide if the region should be retained, based on the free size
216 // in it and the free size in the currently retained region, if any.
217 bool should_retain(HeapRegion* region);
218 protected:
219 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
220 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
221 virtual size_t retire(bool fill_up);
222 public:
223 MutatorAllocRegion()
224 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */),
225 _wasted_bytes(0),
226 _retained_alloc_region(NULL) { }
227
228 // Returns the combined used memory in the current alloc region and
229 // the retained alloc region.
230 size_t used_in_alloc_regions();
231
232 // Perform an allocation out of the retained allocation region, with the given
233 // minimum and desired size. Returns the actual size allocated (between
234 // minimum and desired size) in actual_word_size if the allocation has been
235 // successful.
236 // Should be called without holding a lock. It will try to allocate lock-free
237 // out of the retained region, or return NULL if it was unable to.
238 inline HeapWord* attempt_retained_allocation(size_t min_word_size,
239 size_t desired_word_size,
240 size_t* actual_word_size);
241
242 // This specialization of release() makes sure that the retained alloc
243 // region is retired and set to NULL.
244 virtual HeapRegion* release();
245
246 virtual void init();
247 };
248 // Common base class for allocation regions used during GC.
249 class G1GCAllocRegion : public G1AllocRegion {
250 protected:
251 G1EvacStats* _stats;
252 G1HeapRegionAttr::region_type_t _purpose;
253
254 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
255 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
256
257 virtual size_t retire(bool fill_up);
258
259 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, G1HeapRegionAttr::region_type_t purpose)
260 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
261 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
262 }
263 };
264
265 class SurvivorGCAllocRegion : public G1GCAllocRegion {
266 public:
267 SurvivorGCAllocRegion(G1EvacStats* stats)
268 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, G1HeapRegionAttr::Young) { }
269 };
270
271 class OldGCAllocRegion : public G1GCAllocRegion {
272 public:
273 OldGCAllocRegion(G1EvacStats* stats)
274 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, G1HeapRegionAttr::Old) { }
275
276 // This specialization of release() makes sure that the last card that has
277 // been allocated into has been completely filled by a dummy object. This
278 // avoids races when remembered set scanning wants to update the BOT of the
279 // last card in the retained old gc alloc region, and allocation threads
280 // allocating into that card at the same time.
281 virtual HeapRegion* release();
282 };
283
284 #endif // SHARE_GC_G1_G1ALLOCREGION_HPP