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 size_t used_bytes_before() const { return _used_bytes_before; }
95
96 // Reset the alloc region to point a the dummy region.
97 void reset_alloc_region();
98
99 // Perform a non-MT-safe allocation out of the given region.
100 inline HeapWord* allocate(HeapRegion* alloc_region,
101 size_t word_size);
102
103 // Perform a MT-safe allocation out of the given region.
104 inline HeapWord* par_allocate(HeapRegion* alloc_region,
105 size_t word_size);
106 // Perform a MT-safe allocation out of the given region, with the given
107 // minimum and desired size. Returns the actual size allocated (between
108 // minimum and desired size) in actual_word_size if the allocation has been
109 // successful.
110 inline HeapWord* par_allocate(HeapRegion* alloc_region,
111 size_t min_word_size,
112 size_t desired_word_size,
113 size_t* actual_word_size);
114
115 // Ensure that the region passed as a parameter has been filled up
116 // so that noone else can allocate out of it any more.
117 // Returns the number of bytes that have been wasted by filled up
118 // the space.
119 size_t fill_up_remaining_space(HeapRegion* alloc_region);
120
121 // Retire the active allocating region. If fill_up is true then make
122 // sure that the region is full before we retire it so that no one
123 // else can allocate out of it.
124 // Returns the number of bytes that have been filled up during retire.
125 virtual size_t retire(bool fill_up);
126
127 size_t retire_internal(HeapRegion* alloc_region, bool fill_up, bool forget_used_before = true);
128
129 // For convenience as subclasses use it.
130 static G1CollectedHeap* _g1h;
131
132 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
133 virtual void retire_region(HeapRegion* alloc_region,
134 size_t allocated_bytes) = 0;
135
136 G1AllocRegion(const char* name, bool bot_updates);
137
138 public:
139 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
140
141 HeapRegion* get() const {
142 HeapRegion * hr = _alloc_region;
143 // Make sure that the dummy region does not escape this class.
144 return (hr == _dummy_region) ? NULL : hr;
145 }
146
147 uint count() { return _count; }
148
149 // The following two are the building blocks for the allocation method.
150
151 // First-level allocation: Should be called without holding a
152 // lock. It will try to allocate lock-free out of the active region,
153 // or return NULL if it was unable to.
154 inline HeapWord* attempt_allocation(size_t word_size);
155 // Perform an allocation out of the current allocation region, with the given
156 // minimum and desired size. Returns the actual size allocated (between
157 // minimum and desired size) in actual_word_size if the allocation has been
158 // successful.
159 // Should be called without holding a lock. It will try to allocate lock-free
160 // out of the active region, or return NULL if it was unable to.
161 inline HeapWord* attempt_allocation(size_t min_word_size,
162 size_t desired_word_size,
163 size_t* actual_word_size);
164
165 // Second-level allocation: Should be called while holding a
166 // lock. It will try to first allocate lock-free out of the active
167 // region or, if it's unable to, it will try to replace the active
168 // alloc region with a new one. We require that the caller takes the
169 // appropriate lock before calling this so that it is easier to make
170 // it conform to its locking protocol.
171 inline HeapWord* attempt_allocation_locked(size_t word_size);
172 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
173 // of minimum word size of the block in min_word_size, and the maximum word
174 // size of the allocation in desired_word_size. The actual size of the block is
175 // returned in actual_word_size.
176 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
177 size_t desired_word_size,
178 size_t* actual_word_size);
179
180 // Should be called to allocate a new region even if the max of this
181 // type of regions has been reached. Should only be called if other
182 // allocation attempts have failed and we are not holding a valid
183 // active region.
184 inline HeapWord* attempt_allocation_force(size_t word_size);
185
186 // Should be called before we start using this object.
187 virtual void init();
188
189 // This can be used to set the active region to a specific
190 // region. (Use Example: we try to retain the last old GC alloc
191 // region that we've used during a GC and we can use set() to
192 // re-instate it at the beginning of the next GC.)
193 void set(HeapRegion* alloc_region);
194
195 // Should be called when we want to release the active region which
196 // is returned after it's been retired.
197 virtual HeapRegion* release();
198
199 void trace(const char* str,
200 size_t min_word_size = 0,
201 size_t desired_word_size = 0,
202 size_t actual_word_size = 0,
203 HeapWord* result = NULL) PRODUCT_RETURN;
204 };
205
206 class MutatorAllocRegion : public G1AllocRegion {
207 private:
208 // Keeps track of the total waste generated during the current
209 // mutator phase.
210 size_t _wasted_bytes;
211
212 // Retained allocation region. Used to lower the waste generated
213 // during mutation by having two active regions if the free space
214 // in a region about to be retired still could fit a TLAB.
215 HeapRegion* volatile _retained_alloc_region;
216 size_t _retained_used_bytes_before;
217
218 // Decide if the region should be retained, based on the free size
219 // in it and the free size in the currently retained region, if any.
220 bool should_retain(HeapRegion* region);
221 protected:
222 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
223 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
224 virtual size_t retire(bool fill_up);
225 public:
226 MutatorAllocRegion()
227 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */),
228 _wasted_bytes(0),
229 _retained_alloc_region(NULL),
230 _retained_used_bytes_before(0) { }
231
232 // Returns the combined used memory in the current alloc region and
233 // the retained alloc region.
234 size_t used_in_alloc_regions();
235
236 // Perform an allocation out of the retained allocation region, with the given
237 // minimum and desired size. Returns the actual size allocated (between
238 // minimum and desired size) in actual_word_size if the allocation has been
239 // successful.
240 // Should be called without holding a lock. It will try to allocate lock-free
241 // out of the retained region, or return NULL if it was unable to.
242 inline HeapWord* attempt_retained_allocation(size_t min_word_size,
243 size_t desired_word_size,
244 size_t* actual_word_size);
245
246 // This specialization of release() makes sure that the retained alloc
247 // region is retired and set to NULL.
248 virtual HeapRegion* release();
249
250 virtual void init();
251 };
252 // Common base class for allocation regions used during GC.
253 class G1GCAllocRegion : public G1AllocRegion {
254 protected:
255 G1EvacStats* _stats;
256 G1HeapRegionAttr::region_type_t _purpose;
257
258 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
259 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
260
261 virtual size_t retire(bool fill_up);
262
263 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, G1HeapRegionAttr::region_type_t purpose)
264 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
265 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
266 }
267 };
268
269 class SurvivorGCAllocRegion : public G1GCAllocRegion {
270 public:
271 SurvivorGCAllocRegion(G1EvacStats* stats)
272 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, G1HeapRegionAttr::Young) { }
273
274 static bool should_retain(HeapRegion* region);
275 };
276
277 class OldGCAllocRegion : public G1GCAllocRegion {
278 public:
279 OldGCAllocRegion(G1EvacStats* stats)
280 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, G1HeapRegionAttr::Old) { }
281
282 // This specialization of release() makes sure that the last card that has
283 // been allocated into has been completely filled by a dummy object. This
284 // avoids races when remembered set scanning wants to update the BOT of the
285 // last card in the retained old gc alloc region, and allocation threads
286 // allocating into that card at the same time.
287 virtual HeapRegion* release();
288 };
289
290 #endif // SHARE_GC_G1_G1ALLOCREGION_HPP