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comparison: src/share/vm/gc_implementation/parNew/parGCAllocBuffer.hpp

src/share/vm/gc_implementation/parNew/parGCAllocBuffer.hpp

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1 /*
2 * Copyright (c) 2001, 2010, 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_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/blockOffsetTable.hpp"
30 #include "memory/threadLocalAllocBuffer.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 // Forward decl.
34
35 class PLABStats;
36
37 // A per-thread allocation buffer used during GC.
38 class ParGCAllocBuffer: public CHeapObj<mtGC> {
39 protected:
40 char head[32];
41 size_t _word_sz; // in HeapWord units
42 HeapWord* _bottom;
43 HeapWord* _top;
44 HeapWord* _end; // last allocatable address + 1
45 HeapWord* _hard_end; // _end + AlignmentReserve
46 bool _retained; // whether we hold a _retained_filler
47 MemRegion _retained_filler;
48 // In support of ergonomic sizing of PLAB's
49 size_t _allocated; // in HeapWord units
50 size_t _wasted; // in HeapWord units
51 char tail[32];
52 static size_t FillerHeaderSize;
53 static size_t AlignmentReserve;
54
55 public:
56 // Initializes the buffer to be empty, but with the given "word_sz".
57 // Must get initialized with "set_buf" for an allocation to succeed.
58 ParGCAllocBuffer(size_t word_sz);
59
60 static const size_t min_size() {
61 return ThreadLocalAllocBuffer::min_size();
62 }
63
64 static const size_t max_size() {
65 return ThreadLocalAllocBuffer::max_size();
66 }
67
68 // If an allocation of the given "word_sz" can be satisfied within the
69 // buffer, do the allocation, returning a pointer to the start of the
70 // allocated block. If the allocation request cannot be satisfied,
71 // return NULL.
72 HeapWord* allocate(size_t word_sz) {
73 HeapWord* res = _top;
74 if (pointer_delta(_end, _top) >= word_sz) {
75 _top = _top + word_sz;
76 return res;
77 } else {
78 return NULL;
79 }
80 }
81
82 // Undo the last allocation in the buffer, which is required to be of the
83 // "obj" of the given "word_sz".
84 void undo_allocation(HeapWord* obj, size_t word_sz) {
85 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
86 assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
87 _top = obj;
88 }
89
90 // The total (word) size of the buffer, including both allocated and
91 // unallocted space.
92 size_t word_sz() { return _word_sz; }
93
94 // Should only be done if we are about to reset with a new buffer of the
95 // given size.
96 void set_word_size(size_t new_word_sz) {
97 assert(new_word_sz > AlignmentReserve, "Too small");
98 _word_sz = new_word_sz;
99 }
100
101 // The number of words of unallocated space remaining in the buffer.
102 size_t words_remaining() {
103 assert(_end >= _top, "Negative buffer");
104 return pointer_delta(_end, _top, HeapWordSize);
105 }
106
107 bool contains(void* addr) {
108 return (void*)_bottom <= addr && addr < (void*)_hard_end;
109 }
110
111 // Sets the space of the buffer to be [buf, space+word_sz()).
112 void set_buf(HeapWord* buf) {
113 _bottom = buf;
114 _top = _bottom;
115 _hard_end = _bottom + word_sz();
116 _end = _hard_end - AlignmentReserve;
117 assert(_end >= _top, "Negative buffer");
118 // In support of ergonomic sizing
119 _allocated += word_sz();
120 }
121
122 // Flush the stats supporting ergonomic sizing of PLAB's
123 void flush_stats(PLABStats* stats);
124 void flush_stats_and_retire(PLABStats* stats, bool retain) {
125 // We flush the stats first in order to get a reading of
126 // unused space in the last buffer.
127 if (ResizePLAB) {
128 flush_stats(stats);
129 }
130 // Retire the last allocation buffer.
131 retire(true, retain);
132 }
133
134 // Force future allocations to fail and queries for contains()
135 // to return false
136 void invalidate() {
137 assert(!_retained, "Shouldn't retain an invalidated buffer.");
138 _end = _hard_end;
139 _wasted += pointer_delta(_end, _top); // unused space
140 _top = _end; // force future allocations to fail
141 _bottom = _end; // force future contains() queries to return false
142 }
143
144 // Fills in the unallocated portion of the buffer with a garbage object.
145 // If "end_of_gc" is TRUE, is after the last use in the GC. IF "retain"
146 // is true, attempt to re-use the unused portion in the next GC.
147 void retire(bool end_of_gc, bool retain);
148
149 void print() PRODUCT_RETURN;
150 };
151
152 // PLAB stats book-keeping
153 class PLABStats VALUE_OBJ_CLASS_SPEC {
154 size_t _allocated; // total allocated
155 size_t _wasted; // of which wasted (internal fragmentation)
156 size_t _unused; // Unused in last buffer
157 size_t _used; // derived = allocated - wasted - unused
158 size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized
159 AdaptiveWeightedAverage
160 _filter; // integrator with decay
161
162 public:
163 PLABStats(size_t desired_plab_sz_, unsigned wt) :
164 _allocated(0),
165 _wasted(0),
166 _unused(0),
167 _used(0),
168 _desired_plab_sz(desired_plab_sz_),
169 _filter(wt)
170 {
171 size_t min_sz = min_size();
172 size_t max_sz = max_size();
173 size_t aligned_min_sz = align_object_size(min_sz);
174 size_t aligned_max_sz = align_object_size(max_sz);
175 assert(min_sz <= aligned_min_sz && max_sz >= aligned_max_sz &&
176 min_sz <= max_sz,
177 "PLAB clipping computation in adjust_desired_plab_sz()"
178 " may be incorrect");
179 }
180
181 static const size_t min_size() {
182 return ParGCAllocBuffer::min_size();
183 }
184
185 static const size_t max_size() {
186 return ParGCAllocBuffer::max_size();
187 }
188
189 size_t desired_plab_sz() {
190 return _desired_plab_sz;
191 }
192
193 void adjust_desired_plab_sz(); // filter computation, latches output to
194 // _desired_plab_sz, clears sensor accumulators
195
196 void add_allocated(size_t v) {
197 Atomic::add_ptr(v, &_allocated);
198 }
199
200 void add_unused(size_t v) {
201 Atomic::add_ptr(v, &_unused);
202 }
203
204 void add_wasted(size_t v) {
205 Atomic::add_ptr(v, &_wasted);
206 }
207 };
208
209 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {
210 BlockOffsetArrayContigSpace _bt;
211 BlockOffsetSharedArray* _bsa;
212 HeapWord* _true_end; // end of the whole ParGCAllocBuffer
213
214 static const size_t ChunkSizeInWords;
215 static const size_t ChunkSizeInBytes;
216 HeapWord* allocate_slow(size_t word_sz);
217
218 void fill_region_with_block(MemRegion mr, bool contig);
219
220 public:
221 ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);
222
223 HeapWord* allocate(size_t word_sz) {
224 HeapWord* res = ParGCAllocBuffer::allocate(word_sz);
225 if (res != NULL) {
226 _bt.alloc_block(res, word_sz);
227 } else {
228 res = allocate_slow(word_sz);
229 }
230 return res;
231 }
232
233 void undo_allocation(HeapWord* obj, size_t word_sz);
234
235 void set_buf(HeapWord* buf_start) {
236 ParGCAllocBuffer::set_buf(buf_start);
237 _true_end = _hard_end;
238 _bt.set_region(MemRegion(buf_start, word_sz()));
239 _bt.initialize_threshold();
240 }
241
242 void retire(bool end_of_gc, bool retain);
243
244 MemRegion range() {
245 return MemRegion(_top, _true_end);
246 }
247 };
248
249 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP

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