1 /*
2 * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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 #include "gc/g1/g1MemoryNodeManager.hpp"
32
33 class G1CollectedHeap;
34
35 // A class that holds a region that is active in satisfying allocation
36 // requests, potentially issued in parallel. When the active region is
37 // full it will be retired and replaced with a new one. The
38 // implementation assumes that fast-path allocations will be lock-free
39 // and a lock will need to be taken when the active region needs to be
40 // replaced.
41
42 class G1AllocRegion : public CHeapObj<mtGC> {
43
44 private:
45 // The active allocating region we are currently allocating out
46 // of. The invariant is that if this object is initialized (i.e.,
47 // init() has been called and release() has not) then _alloc_region
48 // is either an active allocating region or the dummy region (i.e.,
49 // it can never be NULL) and this object can be used to satisfy
50 // allocation requests. If this object is not initialized
51 // (i.e. init() has not been called or release() has been called)
52 // then _alloc_region is NULL and this object should not be used to
53 // satisfy allocation requests (it was done this way to force the
54 // correct use of init() and release()).
55 HeapRegion* volatile _alloc_region;
56
57 // It keeps track of the distinct number of regions that are used
58 // for allocation in the active interval of this object, i.e.,
59 // between a call to init() and a call to release(). The count
60 // mostly includes regions that are freshly allocated, as well as
61 // the region that is re-used using the set() method. This count can
62 // be used in any heuristics that might want to bound how many
63 // distinct regions this object can used during an active interval.
64 uint _count;
65
66 // When we set up a new active region we save its used bytes in this
67 // field so that, when we retire it, we can calculate how much space
68 // we allocated in it.
69 size_t _used_bytes_before;
70
71 // When true, indicates that allocate calls should do BOT updates.
72 const bool _bot_updates;
73
74 // Useful for debugging and tracing.
75 const char* _name;
76
77 // A dummy region (i.e., it's been allocated specially for this
78 // purpose and it is not part of the heap) that is full (i.e., top()
79 // == end()). When we don't have a valid active region we make
80 // _alloc_region point to this. This allows us to skip checking
81 // whether the _alloc_region is NULL or not.
82 static HeapRegion* _dummy_region;
83
84 // After a region is allocated by alloc_new_region, this
85 // method is used to set it as the active alloc_region
86 void update_alloc_region(HeapRegion* alloc_region);
87
88 // Allocate a new active region and use it to perform a word_size
89 // allocation. The force parameter will be passed on to
90 // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
91 // to allocate a new region even if the max has been reached.
92 HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
93
94 protected:
95 // The memory node index this allocation region belongs to.
96 uint _node_index;
97
98 // Reset the alloc region to point a the dummy region.
99 void reset_alloc_region();
100
101 // Perform a non-MT-safe allocation out of the given region.
102 inline HeapWord* allocate(HeapRegion* alloc_region,
103 size_t word_size);
104
105 // Perform a MT-safe allocation out of the given region.
106 inline HeapWord* par_allocate(HeapRegion* alloc_region,
107 size_t word_size);
108 // Perform a MT-safe allocation out of the given region, with the given
109 // minimum and desired size. Returns the actual size allocated (between
110 // minimum and desired size) in actual_word_size if the allocation has been
111 // successful.
112 inline HeapWord* par_allocate(HeapRegion* alloc_region,
113 size_t min_word_size,
114 size_t desired_word_size,
115 size_t* actual_word_size);
116
117 // Ensure that the region passed as a parameter has been filled up
118 // so that noone else can allocate out of it any more.
119 // Returns the number of bytes that have been wasted by filled up
120 // the space.
121 size_t fill_up_remaining_space(HeapRegion* alloc_region);
122
123 // Retire the active allocating region. If fill_up is true then make
124 // sure that the region is full before we retire it so that no one
125 // else can allocate out of it.
126 // Returns the number of bytes that have been filled up during retire.
127 virtual size_t retire(bool fill_up);
128
129 size_t retire_internal(HeapRegion* alloc_region, bool fill_up);
130
131 // For convenience as subclasses use it.
132 static G1CollectedHeap* _g1h;
133
134 virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
135 virtual void retire_region(HeapRegion* alloc_region,
136 size_t allocated_bytes) = 0;
137
138 G1AllocRegion(const char* name, bool bot_updates, uint node_index);
139
140 public:
141 static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
142
143 HeapRegion* get() const {
144 HeapRegion * hr = _alloc_region;
145 // Make sure that the dummy region does not escape this class.
146 return (hr == _dummy_region) ? NULL : hr;
147 }
148
149 uint count() { return _count; }
150
151 // The following two are the building blocks for the allocation method.
152
153 // First-level allocation: Should be called without holding a
154 // lock. It will try to allocate lock-free out of the active region,
155 // or return NULL if it was unable to.
156 inline HeapWord* attempt_allocation(size_t word_size);
157 // Perform an allocation out of the current allocation region, with the given
158 // minimum and desired size. Returns the actual size allocated (between
159 // minimum and desired size) in actual_word_size if the allocation has been
160 // successful.
161 // Should be called without holding a lock. It will try to allocate lock-free
162 // out of the active region, or return NULL if it was unable to.
163 inline HeapWord* attempt_allocation(size_t min_word_size,
164 size_t desired_word_size,
165 size_t* actual_word_size);
166
167 // Second-level allocation: Should be called while holding a
168 // lock. It will try to first allocate lock-free out of the active
169 // region or, if it's unable to, it will try to replace the active
170 // alloc region with a new one. We require that the caller takes the
171 // appropriate lock before calling this so that it is easier to make
172 // it conform to its locking protocol.
173 inline HeapWord* attempt_allocation_locked(size_t word_size);
174 // Same as attempt_allocation_locked(size_t, bool), but allowing specification
175 // of minimum word size of the block in min_word_size, and the maximum word
176 // size of the allocation in desired_word_size. The actual size of the block is
177 // returned in actual_word_size.
178 inline HeapWord* attempt_allocation_locked(size_t min_word_size,
179 size_t desired_word_size,
180 size_t* actual_word_size);
181
182 // Should be called to allocate a new region even if the max of this
183 // type of regions has been reached. Should only be called if other
184 // allocation attempts have failed and we are not holding a valid
185 // active region.
186 inline HeapWord* attempt_allocation_force(size_t word_size);
187
188 // Should be called before we start using this object.
189 virtual void init();
190
191 // This can be used to set the active region to a specific
192 // region. (Use Example: we try to retain the last old GC alloc
193 // region that we've used during a GC and we can use set() to
194 // re-instate it at the beginning of the next GC.)
195 void set(HeapRegion* alloc_region);
196
197 // Should be called when we want to release the active region which
198 // is returned after it's been retired.
199 virtual HeapRegion* release();
200
201 void trace(const char* str,
202 size_t min_word_size = 0,
203 size_t desired_word_size = 0,
204 size_t actual_word_size = 0,
205 HeapWord* result = NULL) PRODUCT_RETURN;
206 };
207
208 class MutatorAllocRegion : public G1AllocRegion {
209 private:
210 // Keeps track of the total waste generated during the current
211 // mutator phase.
212 size_t _wasted_bytes;
213
214 // Retained allocation region. Used to lower the waste generated
215 // during mutation by having two active regions if the free space
216 // in a region about to be retired still could fit a TLAB.
217 HeapRegion* volatile _retained_alloc_region;
218
219 // Decide if the region should be retained, based on the free size
220 // in it and the free size in the currently retained region, if any.
221 bool should_retain(HeapRegion* region);
222 protected:
223 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
224 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
225 virtual size_t retire(bool fill_up);
226 public:
227 MutatorAllocRegion(uint node_index)
228 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */, node_index),
229 _wasted_bytes(0),
230 _retained_alloc_region(NULL) { }
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
253 // Common base class for allocation regions used during GC.
254 class G1GCAllocRegion : public G1AllocRegion {
255 protected:
256 G1EvacStats* _stats;
257 G1HeapRegionAttr::region_type_t _purpose;
258
259 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
260 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
261
262 virtual size_t retire(bool fill_up);
263
264 G1GCAllocRegion(const char* name, bool bot_updates, G1EvacStats* stats,
265 G1HeapRegionAttr::region_type_t purpose, uint node_index = G1MemoryNodeManager::AnyNodeIndex)
266 : G1AllocRegion(name, bot_updates, node_index), _stats(stats), _purpose(purpose) {
267 assert(stats != NULL, "Must pass non-NULL PLAB statistics");
268 }
269 };
270
271 class SurvivorGCAllocRegion : public G1GCAllocRegion {
272 public:
273 SurvivorGCAllocRegion(G1EvacStats* stats)
274 : G1GCAllocRegion("Survivor GC Alloc Region", false /* bot_updates */, stats, G1HeapRegionAttr::Young) { }
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