1 /*
2 * Copyright (c) 2001, 2013, 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.
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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 // Flush the stats supporting ergonomic sizing of PLAB's
56 // Should not be called directly
57 void flush_stats(PLABStats* stats);
58
59 public:
60 // Initializes the buffer to be empty, but with the given "word_sz".
61 // Must get initialized with "set_buf" for an allocation to succeed.
62 ParGCAllocBuffer(size_t word_sz);
63 virtual ~ParGCAllocBuffer() {}
64
65 static const size_t min_size() {
66 return ThreadLocalAllocBuffer::min_size();
67 }
68
69 static const size_t max_size() {
70 return ThreadLocalAllocBuffer::max_size();
71 }
72
73 // If an allocation of the given "word_sz" can be satisfied within the
74 // buffer, do the allocation, returning a pointer to the start of the
75 // allocated block. If the allocation request cannot be satisfied,
76 // return NULL.
77 HeapWord* allocate(size_t word_sz) {
78 HeapWord* res = _top;
79 if (pointer_delta(_end, _top) >= word_sz) {
80 _top = _top + word_sz;
81 return res;
82 } else {
83 return NULL;
84 }
85 }
86
87 // Undo the last allocation in the buffer, which is required to be of the
88 // "obj" of the given "word_sz".
89 void undo_allocation(HeapWord* obj, size_t word_sz) {
90 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
91 assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
92 _top = obj;
93 }
94
95 // The total (word) size of the buffer, including both allocated and
96 // unallocted space.
97 size_t word_sz() { return _word_sz; }
98
99 // Should only be done if we are about to reset with a new buffer of the
100 // given size.
101 void set_word_size(size_t new_word_sz) {
102 assert(new_word_sz > AlignmentReserve, "Too small");
103 _word_sz = new_word_sz;
104 }
105
106 // The number of words of unallocated space remaining in the buffer.
107 size_t words_remaining() {
108 assert(_end >= _top, "Negative buffer");
109 return pointer_delta(_end, _top, HeapWordSize);
110 }
111
112 bool contains(void* addr) {
113 return (void*)_bottom <= addr && addr < (void*)_hard_end;
114 }
115
116 // Sets the space of the buffer to be [buf, space+word_sz()).
117 virtual void set_buf(HeapWord* buf) {
118 _bottom = buf;
119 _top = _bottom;
120 _hard_end = _bottom + word_sz();
121 _end = _hard_end - AlignmentReserve;
122 assert(_end >= _top, "Negative buffer");
123 // In support of ergonomic sizing
124 _allocated += word_sz();
125 }
126
127 // Flush the stats supporting ergonomic sizing of PLAB's
128 // and retire the current buffer.
129 void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, bool retain) {
130 // We flush the stats first in order to get a reading of
131 // unused space in the last buffer.
132 if (ResizePLAB) {
133 flush_stats(stats);
134
135 // Since we have flushed the stats we need to clear
136 // the _allocated and _wasted fields. Not doing so
137 // will artifically inflate the values in the stats
138 // to which we add them.
139 // The next time we flush these values, we will add
140 // what we have just flushed in addition to the size
141 // of the buffers allocated between now and then.
142 _allocated = 0;
143 _wasted = 0;
144 }
145 // Retire the last allocation buffer.
146 retire(end_of_gc, retain);
147 }
148
149 // Force future allocations to fail and queries for contains()
150 // to return false
151 void invalidate() {
152 assert(!_retained, "Shouldn't retain an invalidated buffer.");
153 _end = _hard_end;
154 _wasted += pointer_delta(_end, _top); // unused space
155 _top = _end; // force future allocations to fail
156 _bottom = _end; // force future contains() queries to return false
157 }
158
159 // Fills in the unallocated portion of the buffer with a garbage object.
160 // If "end_of_gc" is TRUE, is after the last use in the GC. IF "retain"
161 // is true, attempt to re-use the unused portion in the next GC.
162 virtual void retire(bool end_of_gc, bool retain);
163
164 void print() PRODUCT_RETURN;
165 };
166
167 // PLAB stats book-keeping
168 class PLABStats VALUE_OBJ_CLASS_SPEC {
169 size_t _allocated; // total allocated
170 size_t _wasted; // of which wasted (internal fragmentation)
171 size_t _unused; // Unused in last buffer
172 size_t _used; // derived = allocated - wasted - unused
173 size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized
174 AdaptiveWeightedAverage
175 _filter; // integrator with decay
176
177 public:
178 PLABStats(size_t desired_plab_sz_, unsigned wt) :
179 _allocated(0),
180 _wasted(0),
181 _unused(0),
182 _used(0),
183 _desired_plab_sz(desired_plab_sz_),
184 _filter(wt)
185 { }
186
187 static const size_t min_size() {
188 return ParGCAllocBuffer::min_size();
189 }
190
191 static const size_t max_size() {
192 return ParGCAllocBuffer::max_size();
193 }
194
195 size_t desired_plab_sz() {
196 return _desired_plab_sz;
197 }
198
199 void adjust_desired_plab_sz(uint no_of_gc_workers);
200 // filter computation, latches output to
201 // _desired_plab_sz, clears sensor accumulators
202
203 void add_allocated(size_t v) {
204 Atomic::add_ptr(v, &_allocated);
205 }
206
207 void add_unused(size_t v) {
208 Atomic::add_ptr(v, &_unused);
209 }
210
211 void add_wasted(size_t v) {
212 Atomic::add_ptr(v, &_wasted);
213 }
214 };
215
216 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {
217 BlockOffsetArrayContigSpace _bt;
218 BlockOffsetSharedArray* _bsa;
219 HeapWord* _true_end; // end of the whole ParGCAllocBuffer
220
221 static const size_t ChunkSizeInWords;
222 static const size_t ChunkSizeInBytes;
223 HeapWord* allocate_slow(size_t word_sz);
224
225 void fill_region_with_block(MemRegion mr, bool contig);
226
227 public:
228 ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);
229
230 HeapWord* allocate(size_t word_sz) {
231 HeapWord* res = ParGCAllocBuffer::allocate(word_sz);
232 if (res != NULL) {
233 _bt.alloc_block(res, word_sz);
234 } else {
235 res = allocate_slow(word_sz);
236 }
237 return res;
238 }
239
240 void undo_allocation(HeapWord* obj, size_t word_sz);
241
242 virtual void set_buf(HeapWord* buf_start) {
243 ParGCAllocBuffer::set_buf(buf_start);
244 _true_end = _hard_end;
245 _bt.set_region(MemRegion(buf_start, word_sz()));
246 _bt.initialize_threshold();
247 }
248
249 virtual void retire(bool end_of_gc, bool retain);
250
251 MemRegion range() {
252 return MemRegion(_top, _true_end);
253 }
254 };
255
256 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP