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 // 0 -> no tracing, 1 -> basic tracing, 2 -> basic + allocation tracing
35 #define G1_ALLOC_REGION_TRACING 0
36
37 // A class that holds a region that is active in satisfying allocation
38 // requests, potentially issued in parallel. When the active region is
39 // full it will be retired and replaced with a new one. The
40 // implementation assumes that fast-path allocations will be lock-free
41 // and a lock will need to be taken when the active region needs to be
42 // replaced.
43
44 class G1AllocRegion VALUE_OBJ_CLASS_SPEC {
45
46 private:
47 // The active allocating region we are currently allocating out
48 // of. The invariant is that if this object is initialized (i.e.,
49 // init() has been called and release() has not) then _alloc_region
50 // is either an active allocating region or the dummy region (i.e.,
51 // it can never be NULL) and this object can be used to satisfy
52 // allocation requests. If this object is not initialized
53 // (i.e. init() has not been called or release() has been called)
54 // then _alloc_region is NULL and this object should not be used to
55 // satisfy allocation requests (it was done this way to force the
56 // correct use of init() and release()).
57 HeapRegion* volatile _alloc_region;
58
59 // Allocation context associated with this alloc region.
60 AllocationContext_t _allocation_context;
61
62 // It keeps track of the distinct number of regions that are used
63 // for allocation in the active interval of this object, i.e.,
64 // between a call to init() and a call to release(). The count
65 // mostly includes regions that are freshly allocated, as well as
66 // the region that is re-used using the set() method. This count can
67 // be used in any heuristics that might want to bound how many
68 // distinct regions this object can used during an active interval.
69 uint _count;
70
71 // When we set up a new active region we save its used bytes in this
72 // field so that, when we retire it, we can calculate how much space
73 // we allocated in it.
74 size_t _used_bytes_before;
75
76 // When true, indicates that allocate calls should do BOT updates.
77 const bool _bot_updates;
78
79 // Useful for debugging and tracing.
80 const char* _name;
81
82 // A dummy region (i.e., it's been allocated specially for this
83 // purpose and it is not part of the heap) that is full (i.e., top()
84 // == end()). When we don't have a valid active region we make
85 // _alloc_region point to this. This allows us to skip checking
86 // whether the _alloc_region is NULL or not.
87 static HeapRegion* _dummy_region;
88
89 // Some of the methods below take a bot_updates parameter. Its value
90 // should be the same as the _bot_updates field. The idea is that
91 // the parameter will be a constant for a particular alloc region
92 // and, given that these methods will be hopefully inlined, the
93 // compiler should compile out the test.
94
95 // Perform a non-MT-safe allocation out of the given region.
96 static inline HeapWord* allocate(HeapRegion* alloc_region,
97 size_t word_size,
98 bool bot_updates);
99
100 // Perform a MT-safe allocation out of the given region.
101 static inline HeapWord* par_allocate(HeapRegion* alloc_region,
102 size_t word_size,
103 bool bot_updates);
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 static 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 bool bot_updates);
113
114 // Ensure that the region passed as a parameter has been filled up
115 // so that noone else can allocate out of it any more.
116 // Returns the number of bytes that have been wasted by filled up
117 // the space.
118 static size_t fill_up_remaining_space(HeapRegion* alloc_region,
119 bool bot_updates);
120
121 // After a region is allocated by alloc_new_region, this
122 // method is used to set it as the active alloc_region
123 void update_alloc_region(HeapRegion* alloc_region);
124
125 // Allocate a new active region and use it to perform a word_size
126 // allocation. The force parameter will be passed on to
127 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
128 // to allocate a new region even if the max has been reached.
129 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
130
131 protected:
132 // Retire the active allocating region. If fill_up is true then make
133 // sure that the region is full before we retire it so that no one
134 // else can allocate out of it.
135 // Returns the number of bytes that have been filled up during retire.
136 virtual size_t retire(bool fill_up);
137
138 // For convenience as subclasses use it.
139 static G1CollectedHeap* _g1h;
140
141 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
142 virtual void retire_region(HeapRegion* alloc_region,
143 size_t allocated_bytes) = 0;
144
145 G1AllocRegion(const char* name, bool bot_updates);
146
147 public:
148 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
149
150 HeapRegion* get() const {
151 HeapRegion * hr = _alloc_region;
152 // Make sure that the dummy region does not escape this class.
153 return (hr == _dummy_region) ? NULL : hr;
154 }
155
156 void set_allocation_context(AllocationContext_t context) { _allocation_context = context; }
157 AllocationContext_t allocation_context() { return _allocation_context; }
158
159 uint count() { return _count; }
160
161 // The following two are the building blocks for the allocation method.
162
163 // First-level allocation: Should be called without holding a
164 // lock. It will try to allocate lock-free out of the active region,
165 // or return NULL if it was unable to.
166 inline HeapWord* attempt_allocation(size_t word_size,
167 bool bot_updates);
168 // Perform an allocation out of the current allocation region, with the given
169 // minimum and desired size. Returns the actual size allocated (between
170 // minimum and desired size) in actual_word_size if the allocation has been
171 // successful.
172 // Should be called without holding a lock. It will try to allocate lock-free
173 // out of the active region, or return NULL if it was unable to.
174 inline HeapWord* attempt_allocation(size_t min_word_size,
175 size_t desired_word_size,
176 size_t* actual_word_size,
177 bool bot_updates);
178
179 // Second-level allocation: Should be called while holding a
180 // lock. It will try to first allocate lock-free out of the active
181 // region or, if it's unable to, it will try to replace the active
182 // alloc region with a new one. We require that the caller takes the
183 // appropriate lock before calling this so that it is easier to make
184 // it conform to its locking protocol.
185 inline HeapWord* attempt_allocation_locked(size_t word_size,
186 bool bot_updates);
187 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
188 // of minimum word size of the block in min_word_size, and the maximum word
189 // size of the allocation in desired_word_size. The actual size of the block is
190 // returned in actual_word_size.
191 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
192 size_t desired_word_size,
193 size_t* actual_word_size,
194 bool bot_updates);
195
196 // Should be called to allocate a new region even if the max of this
197 // type of regions has been reached. Should only be called if other
198 // allocation attempts have failed and we are not holding a valid
199 // active region.
200 inline HeapWord* attempt_allocation_force(size_t word_size,
201 bool bot_updates);
202
203 // Should be called before we start using this object.
204 void init();
205
206 // This can be used to set the active region to a specific
207 // region. (Use Example: we try to retain the last old GC alloc
208 // region that we've used during a GC and we can use set() to
209 // re-instate it at the beginning of the next GC.)
210 void set(HeapRegion* alloc_region);
211
212 // Should be called when we want to release the active region which
213 // is returned after it's been retired.
214 virtual HeapRegion* release();
215
216 #if G1_ALLOC_REGION_TRACING
217 void trace(const char* str,
218 size_t min_word_size = 0,
219 size_t desired_word_size = 0,
220 size_t actual_word_size = 0,
221 HeapWord* result = NULL);
222 #else // G1_ALLOC_REGION_TRACING
223 void trace(const char* str,
224 size_t min_word_size = 0,
225 size_t desired_word_size = 0,
226 size_t actual_word_size = 0,
227 HeapWord* result = NULL) { }
228 #endif // G1_ALLOC_REGION_TRACING
229 };
230
231 class MutatorAllocRegion : public G1AllocRegion {
232 protected:
233 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
234 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
235 public:
236 MutatorAllocRegion()
237 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
238 };
239
240 // Common base class for allocation regions used during GC.
241 class G1GCAllocRegion : public G1AllocRegion {
242 protected:
243 G1EvacStats* _stats;
244 InCSetState::in_cset_state_t _purpose;
245
246 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
247 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
248
249 virtual size_t retire(bool fill_up);
250 public:
251 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats, InCSetState::in_cset_state_t purpose)
252 : G1AllocRegion(name, bot_updates), _stats(stats), _purpose(purpose) {
253 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
254 }
255 };
256
257 class SurvivorGCAllocRegion : public G1GCAllocRegion {
258 public:
259 SurvivorGCAllocRegion(G1EvacStats* stats)
260 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, InCSetState::Young) { }
261 };
262
263 class OldGCAllocRegion : public G1GCAllocRegion {
264 public:
265 OldGCAllocRegion(G1EvacStats* stats)
266 : G1GCAllocRegion("Old GC Alloc Region", true /* bot_updates */, stats, InCSetState::Old) { }
267
268 // This specialization of release() makes sure that the last card that has
269 // been allocated into has been completely filled by a dummy object. This
270 // avoids races when remembered set scanning wants to update the BOT of the
271 // last card in the retained old gc alloc region, and allocation threads
272 // allocating into that card at the same time.
273 virtual HeapRegion* release();
274 };
275
276 #endif // SHARE_VM_GC_G1_G1ALLOCREGION_HPP