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comparison src/share/vm/gc_implementation/parNew/parGCAllocBuffer.hpp @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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1 /*
2 * Copyright 2001-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 // Forward decl.
26
27 class PLABStats;
28
29 // A per-thread allocation buffer used during GC.
30 class ParGCAllocBuffer: public CHeapObj {
31 protected:
32 char head[32];
33 size_t _word_sz; // in HeapWord units
34 HeapWord* _bottom;
35 HeapWord* _top;
36 HeapWord* _end; // last allocatable address + 1
37 HeapWord* _hard_end; // _end + AlignmentReserve
38 bool _retained; // whether we hold a _retained_filler
39 MemRegion _retained_filler;
40 // In support of ergonomic sizing of PLAB's
41 size_t _allocated; // in HeapWord units
42 size_t _wasted; // in HeapWord units
43 char tail[32];
44 static const size_t FillerHeaderSize;
45 static const size_t AlignmentReserve;
46
47 public:
48 // Initializes the buffer to be empty, but with the given "word_sz".
49 // Must get initialized with "set_buf" for an allocation to succeed.
50 ParGCAllocBuffer(size_t word_sz);
51
52 static const size_t min_size() {
53 return ThreadLocalAllocBuffer::min_size();
54 }
55
56 static const size_t max_size() {
57 return ThreadLocalAllocBuffer::max_size();
58 }
59
60 // If an allocation of the given "word_sz" can be satisfied within the
61 // buffer, do the allocation, returning a pointer to the start of the
62 // allocated block. If the allocation request cannot be satisfied,
63 // return NULL.
64 HeapWord* allocate(size_t word_sz) {
65 HeapWord* res = _top;
66 HeapWord* new_top = _top + word_sz;
67 if (new_top <= _end) {
68 _top = new_top;
69 return res;
70 } else {
71 return NULL;
72 }
73 }
74
75 // Undo the last allocation in the buffer, which is required to be of the
76 // "obj" of the given "word_sz".
77 void undo_allocation(HeapWord* obj, size_t word_sz) {
78 assert(_top - word_sz >= _bottom
79 && _top - word_sz == obj,
80 "Bad undo_allocation");
81 _top = _top - word_sz;
82 }
83
84 // The total (word) size of the buffer, including both allocated and
85 // unallocted space.
86 size_t word_sz() { return _word_sz; }
87
88 // Should only be done if we are about to reset with a new buffer of the
89 // given size.
90 void set_word_size(size_t new_word_sz) {
91 assert(new_word_sz > AlignmentReserve, "Too small");
92 _word_sz = new_word_sz;
93 }
94
95 // The number of words of unallocated space remaining in the buffer.
96 size_t words_remaining() {
97 assert(_end >= _top, "Negative buffer");
98 return pointer_delta(_end, _top, HeapWordSize);
99 }
100
101 bool contains(void* addr) {
102 return (void*)_bottom <= addr && addr < (void*)_hard_end;
103 }
104
105 // Sets the space of the buffer to be [buf, space+word_sz()).
106 void set_buf(HeapWord* buf) {
107 _bottom = buf;
108 _top = _bottom;
109 _hard_end = _bottom + word_sz();
110 _end = _hard_end - AlignmentReserve;
111 assert(_end >= _top, "Negative buffer");
112 // In support of ergonomic sizing
113 _allocated += word_sz();
114 }
115
116 // Flush the stats supporting ergonomic sizing of PLAB's
117 void flush_stats(PLABStats* stats);
118 void flush_stats_and_retire(PLABStats* stats, bool retain) {
119 // We flush the stats first in order to get a reading of
120 // unused space in the last buffer.
121 if (ResizePLAB) {
122 flush_stats(stats);
123 }
124 // Retire the last allocation buffer.
125 retire(true, retain);
126 }
127
128 // Force future allocations to fail and queries for contains()
129 // to return false
130 void invalidate() {
131 assert(!_retained, "Shouldn't retain an invalidated buffer.");
132 _end = _hard_end;
133 _wasted += pointer_delta(_end, _top); // unused space
134 _top = _end; // force future allocations to fail
135 _bottom = _end; // force future contains() queries to return false
136 }
137
138 // Fills in the unallocated portion of the buffer with a garbage object.
139 // If "end_of_gc" is TRUE, is after the last use in the GC. IF "retain"
140 // is true, attempt to re-use the unused portion in the next GC.
141 void retire(bool end_of_gc, bool retain);
142
143 void print() PRODUCT_RETURN;
144 };
145
146 // PLAB stats book-keeping
147 class PLABStats VALUE_OBJ_CLASS_SPEC {
148 size_t _allocated; // total allocated
149 size_t _wasted; // of which wasted (internal fragmentation)
150 size_t _unused; // Unused in last buffer
151 size_t _used; // derived = allocated - wasted - unused
152 size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized
153 AdaptiveWeightedAverage
154 _filter; // integrator with decay
155
156 public:
157 PLABStats(size_t desired_plab_sz_, unsigned wt) :
158 _allocated(0),
159 _wasted(0),
160 _unused(0),
161 _used(0),
162 _desired_plab_sz(desired_plab_sz_),
163 _filter(wt)
164 {
165 size_t min_sz = min_size();
166 size_t max_sz = max_size();
167 size_t aligned_min_sz = align_object_size(min_sz);
168 size_t aligned_max_sz = align_object_size(max_sz);
169 assert(min_sz <= aligned_min_sz && max_sz >= aligned_max_sz &&
170 min_sz <= max_sz,
171 "PLAB clipping computation in adjust_desired_plab_sz()"
172 " may be incorrect");
173 }
174
175 static const size_t min_size() {
176 return ParGCAllocBuffer::min_size();
177 }
178
179 static const size_t max_size() {
180 return ParGCAllocBuffer::max_size();
181 }
182
183 size_t desired_plab_sz() {
184 return _desired_plab_sz;
185 }
186
187 void adjust_desired_plab_sz(); // filter computation, latches output to
188 // _desired_plab_sz, clears sensor accumulators
189
190 void add_allocated(size_t v) {
191 Atomic::add_ptr(v, &_allocated);
192 }
193
194 void add_unused(size_t v) {
195 Atomic::add_ptr(v, &_unused);
196 }
197
198 void add_wasted(size_t v) {
199 Atomic::add_ptr(v, &_wasted);
200 }
201 };
202
203 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {
204 BlockOffsetArrayContigSpace _bt;
205 BlockOffsetSharedArray* _bsa;
206 HeapWord* _true_end; // end of the whole ParGCAllocBuffer
207
208 static const size_t ChunkSizeInWords;
209 static const size_t ChunkSizeInBytes;
210 HeapWord* allocate_slow(size_t word_sz);
211
212 void fill_region_with_block(MemRegion mr, bool contig);
213
214 public:
215 ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);
216
217 HeapWord* allocate(size_t word_sz) {
218 HeapWord* res = ParGCAllocBuffer::allocate(word_sz);
219 if (res != NULL) {
220 _bt.alloc_block(res, word_sz);
221 } else {
222 res = allocate_slow(word_sz);
223 }
224 return res;
225 }
226
227 void undo_allocation(HeapWord* obj, size_t word_sz);
228
229 void set_buf(HeapWord* buf_start) {
230 ParGCAllocBuffer::set_buf(buf_start);
231 _true_end = _hard_end;
232 _bt.set_region(MemRegion(buf_start, word_sz()));
233 _bt.initialize_threshold();
234 }
235
236 void retire(bool end_of_gc, bool retain);
237
238 MemRegion range() {
239 return MemRegion(_top, _true_end);
240 }
241 };