1 /*
2 * Copyright (c) 2001, 2009, 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 // 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 size_t FillerHeaderSize;
45 static 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 if (pointer_delta(_end, _top) >= word_sz) {
67 _top = _top + word_sz;
68 return res;
69 } else {
70 return NULL;
71 }
72 }
73
74 // Undo the last allocation in the buffer, which is required to be of the
75 // "obj" of the given "word_sz".
76 void undo_allocation(HeapWord* obj, size_t word_sz) {
77 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
78 assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
79 _top = obj;
80 }
81
82 // The total (word) size of the buffer, including both allocated and
83 // unallocted space.
84 size_t word_sz() { return _word_sz; }
85
86 // Should only be done if we are about to reset with a new buffer of the
87 // given size.
88 void set_word_size(size_t new_word_sz) {
89 assert(new_word_sz > AlignmentReserve, "Too small");
90 _word_sz = new_word_sz;
91 }
92
93 // The number of words of unallocated space remaining in the buffer.
94 size_t words_remaining() {
95 assert(_end >= _top, "Negative buffer");
96 return pointer_delta(_end, _top, HeapWordSize);
97 }
98
99 bool contains(void* addr) {
100 return (void*)_bottom <= addr && addr < (void*)_hard_end;
101 }
102
103 // Sets the space of the buffer to be [buf, space+word_sz()).
104 void set_buf(HeapWord* buf) {
105 _bottom = buf;
106 _top = _bottom;
107 _hard_end = _bottom + word_sz();
108 _end = _hard_end - AlignmentReserve;
109 assert(_end >= _top, "Negative buffer");
110 // In support of ergonomic sizing
111 _allocated += word_sz();
112 }
113
114 // Flush the stats supporting ergonomic sizing of PLAB's
115 void flush_stats(PLABStats* stats);
116 void flush_stats_and_retire(PLABStats* stats, bool retain) {
117 // We flush the stats first in order to get a reading of
118 // unused space in the last buffer.
119 if (ResizePLAB) {
120 flush_stats(stats);
121 }
122 // Retire the last allocation buffer.
123 retire(true, retain);
124 }
125
126 // Force future allocations to fail and queries for contains()
127 // to return false
128 void invalidate() {
129 assert(!_retained, "Shouldn't retain an invalidated buffer.");
130 _end = _hard_end;
131 _wasted += pointer_delta(_end, _top); // unused space
132 _top = _end; // force future allocations to fail
133 _bottom = _end; // force future contains() queries to return false
134 }
135
136 // Fills in the unallocated portion of the buffer with a garbage object.
137 // If "end_of_gc" is TRUE, is after the last use in the GC. IF "retain"
138 // is true, attempt to re-use the unused portion in the next GC.
139 void retire(bool end_of_gc, bool retain);
140
141 void print() PRODUCT_RETURN;
142 };
143
144 // PLAB stats book-keeping
145 class PLABStats VALUE_OBJ_CLASS_SPEC {
146 size_t _allocated; // total allocated
147 size_t _wasted; // of which wasted (internal fragmentation)
148 size_t _unused; // Unused in last buffer
149 size_t _used; // derived = allocated - wasted - unused
150 size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized
151 AdaptiveWeightedAverage
152 _filter; // integrator with decay
153
154 public:
155 PLABStats(size_t desired_plab_sz_, unsigned wt) :
156 _allocated(0),
157 _wasted(0),
158 _unused(0),
159 _used(0),
160 _desired_plab_sz(desired_plab_sz_),
161 _filter(wt)
162 {
163 size_t min_sz = min_size();
164 size_t max_sz = max_size();
165 size_t aligned_min_sz = align_object_size(min_sz);
166 size_t aligned_max_sz = align_object_size(max_sz);
167 assert(min_sz <= aligned_min_sz && max_sz >= aligned_max_sz &&
168 min_sz <= max_sz,
169 "PLAB clipping computation in adjust_desired_plab_sz()"
170 " may be incorrect");
171 }
172
173 static const size_t min_size() {
174 return ParGCAllocBuffer::min_size();
175 }
176
177 static const size_t max_size() {
178 return ParGCAllocBuffer::max_size();
179 }
180
181 size_t desired_plab_sz() {
182 return _desired_plab_sz;
183 }
184
185 void adjust_desired_plab_sz(); // filter computation, latches output to
186 // _desired_plab_sz, clears sensor accumulators
187
188 void add_allocated(size_t v) {
189 Atomic::add_ptr(v, &_allocated);
190 }
191
192 void add_unused(size_t v) {
193 Atomic::add_ptr(v, &_unused);
194 }
195
196 void add_wasted(size_t v) {
197 Atomic::add_ptr(v, &_wasted);
198 }
199 };
200
201 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {
202 BlockOffsetArrayContigSpace _bt;
203 BlockOffsetSharedArray* _bsa;
204 HeapWord* _true_end; // end of the whole ParGCAllocBuffer
205
206 static const size_t ChunkSizeInWords;
207 static const size_t ChunkSizeInBytes;
208 HeapWord* allocate_slow(size_t word_sz);
209
210 void fill_region_with_block(MemRegion mr, bool contig);
211
212 public:
213 ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);
214
215 HeapWord* allocate(size_t word_sz) {
216 HeapWord* res = ParGCAllocBuffer::allocate(word_sz);
217 if (res != NULL) {
218 _bt.alloc_block(res, word_sz);
219 } else {
220 res = allocate_slow(word_sz);
221 }
222 return res;
223 }
224
225 void undo_allocation(HeapWord* obj, size_t word_sz);
226
227 void set_buf(HeapWord* buf_start) {
228 ParGCAllocBuffer::set_buf(buf_start);
229 _true_end = _hard_end;
230 _bt.set_region(MemRegion(buf_start, word_sz()));
231 _bt.initialize_threshold();
232 }
233
234 void retire(bool end_of_gc, bool retain);
235
236 MemRegion range() {
237 return MemRegion(_top, _true_end);
238 }
239 };