1 /*
2 * Copyright (c) 2001, 2015, 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.
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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
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23 */
24
25 #ifndef SHARE_VM_GC_SHARED_PLAB_HPP
26 #define SHARE_VM_GC_SHARED_PLAB_HPP
27
28 #include "gc/shared/gcUtil.hpp"
29 #include "memory/allocation.hpp"
30 #include "utilities/globalDefinitions.hpp"
31
32 // Forward declarations.
33 class PLABStats;
34
35 // A per-thread allocation buffer used during GC.
36 class PLAB: public CHeapObj<mtGC> {
37 protected:
38 char head[32];
39 size_t _word_sz; // In HeapWord units
40 HeapWord* _bottom;
41 HeapWord* _top;
42 HeapWord* _end; // Last allocatable address + 1
43 HeapWord* _hard_end; // _end + AlignmentReserve
44 // In support of ergonomic sizing of PLAB's
45 size_t _allocated; // in HeapWord units
46 size_t _wasted; // in HeapWord units
47 size_t _undo_wasted;
48 char tail[32];
49 static size_t AlignmentReserve;
50
51 // Force future allocations to fail and queries for contains()
52 // to return false. Returns the amount of unused space in this PLAB.
53 size_t invalidate() {
54 _end = _hard_end;
55 size_t remaining = pointer_delta(_end, _top); // Calculate remaining space.
56 _top = _end; // Force future allocations to fail.
57 _bottom = _end; // Force future contains() queries to return false.
58 return remaining;
59 }
60
61 // Fill in remaining space with a dummy object and invalidate the PLAB. Returns
62 // the amount of remaining space.
63 size_t retire_internal();
64
65 void add_undo_waste(HeapWord* obj, size_t word_sz);
66
67 // Undo the last allocation in the buffer, which is required to be of the
68 // "obj" of the given "word_sz".
69 void undo_last_allocation(HeapWord* obj, size_t word_sz);
70
71 public:
72 // Initializes the buffer to be empty, but with the given "word_sz".
73 // Must get initialized with "set_buf" for an allocation to succeed.
74 PLAB(size_t word_sz);
75 virtual ~PLAB() {}
76
77 // Minimum PLAB size.
78 static size_t min_size();
79 // Maximum PLAB size.
80 static size_t max_size();
81
82 // If an allocation of the given "word_sz" can be satisfied within the
83 // buffer, do the allocation, returning a pointer to the start of the
84 // allocated block. If the allocation request cannot be satisfied,
85 // return NULL.
86 HeapWord* allocate(size_t word_sz) {
87 HeapWord* res = _top;
88 if (pointer_delta(_end, _top) >= word_sz) {
89 _top = _top + word_sz;
90 return res;
91 } else {
92 return NULL;
93 }
94 }
95
96 // Allocate the object aligned to "alignment_in_bytes".
97 inline HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);
98
99 // Undo any allocation in the buffer, which is required to be of the
100 // "obj" of the given "word_sz".
101 void undo_allocation(HeapWord* obj, size_t word_sz);
102
103 // The total (word) size of the buffer, including both allocated and
104 // unallocated space.
105 size_t word_sz() { return _word_sz; }
106
107 size_t waste() { return _wasted; }
108 size_t undo_waste() { return _undo_wasted; }
109
110 // Should only be done if we are about to reset with a new buffer of the
111 // given size.
112 void set_word_size(size_t new_word_sz) {
113 assert(new_word_sz > AlignmentReserve, "Too small");
114 _word_sz = new_word_sz;
115 }
116
117 // The number of words of unallocated space remaining in the buffer.
118 size_t words_remaining() {
119 assert(_end >= _top, "Negative buffer");
120 return pointer_delta(_end, _top, HeapWordSize);
121 }
122
123 bool contains(void* addr) {
124 return (void*)_bottom <= addr && addr < (void*)_hard_end;
125 }
126
127 // Sets the space of the buffer to be [buf, space+word_sz()).
128 virtual void set_buf(HeapWord* buf) {
129 _bottom = buf;
130 _top = _bottom;
131 _hard_end = _bottom + word_sz();
132 _end = _hard_end - AlignmentReserve;
133 assert(_end >= _top, "Negative buffer");
134 // In support of ergonomic sizing
135 _allocated += word_sz();
136 }
137
138 // Flush allocation statistics into the given PLABStats supporting ergonomic
139 // sizing of PLAB's and retire the current buffer. To be called at the end of
140 // GC.
141 virtual void flush_and_retire_stats(PLABStats* stats);
142
143 // Fills in the unallocated portion of the buffer with a garbage object and updates
144 // statistics. To be called during GC.
145 virtual void retire();
146
147 void print() PRODUCT_RETURN;
148 };
149
150 // PLAB book-keeping.
151 class PLABStats : public CHeapObj<mtGC> {
152 protected:
153 size_t _allocated; // Total allocated
154 size_t _wasted; // of which wasted (internal fragmentation)
155 size_t _undo_wasted; // of which wasted on undo (is not used for calculation of PLAB size)
156 size_t _unused; // Unused in last buffer
157 size_t _desired_net_plab_sz;// Output of filter (below), suitably trimmed and quantized
158 AdaptiveWeightedAverage
159 _filter; // Integrator with decay
160
161 virtual void reset() {
162 _allocated = 0;
163 _wasted = 0;
164 _undo_wasted = 0;
165 _unused = 0;
166 }
167 public:
168 PLABStats(size_t desired_net_plab_sz_, unsigned wt) :
169 _allocated(0),
170 _wasted(0),
171 _undo_wasted(0),
172 _unused(0),
173 _desired_net_plab_sz(desired_net_plab_sz_),
174 _filter(wt)
175 { }
176
177 virtual ~PLABStats() { }
178
179 static const size_t min_size() {
180 return PLAB::min_size();
181 }
182
183 static const size_t max_size() {
184 return PLAB::max_size();
185 }
186
187 // Calculates plab size for current number of gc worker threads.
188 size_t desired_plab_sz(uint no_of_gc_workers);
189
190 // Updates the current desired PLAB size. Computes the new desired PLAB size with one gc worker thread,
191 // updates _desired_plab_sz and clears sensor accumulators.
192 virtual void adjust_desired_plab_sz();
193
194 inline void add_allocated(size_t v);
195
196 inline void add_unused(size_t v);
197
198 inline void add_wasted(size_t v);
199
200 inline void add_undo_wasted(size_t v);
201 };
202
203 #endif // SHARE_VM_GC_SHARED_PLAB_HPP