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 static size_t alignment_reserve() { return AlignmentReserve; }
78
79 // Minimum PLAB size.
80 static size_t min_size();
81 // Maximum PLAB size.
82 static size_t max_size();
83
84 // If an allocation of the given "word_sz" can be satisfied within the
85 // buffer, do the allocation, returning a pointer to the start of the
86 // allocated block. If the allocation request cannot be satisfied,
87 // return NULL.
88 HeapWord* allocate(size_t word_sz) {
89 HeapWord* res = _top;
90 if (pointer_delta(_end, _top) >= word_sz) {
91 _top = _top + word_sz;
92 return res;
93 } else {
94 return NULL;
95 }
96 }
97
98 // Allocate the object aligned to "alignment_in_bytes".
99 inline HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);
100
101 // Undo any allocation in the buffer, which is required to be of the
102 // "obj" of the given "word_sz".
103 void undo_allocation(HeapWord* obj, size_t word_sz);
104
105 // The total (word) size of the buffer, including both allocated and
106 // unallocated space.
107 size_t word_sz() { return _word_sz; }
108
109 size_t waste() { return _wasted; }
110 size_t undo_waste() { return _undo_wasted; }
111
112 // Should only be done if we are about to reset with a new buffer of the
113 // given size.
114 void set_word_size(size_t new_word_sz) {
115 assert(new_word_sz > AlignmentReserve, "Too small");
116 _word_sz = new_word_sz;
117 }
118
119 // The number of words of unallocated space remaining in the buffer.
120 size_t words_remaining() {
121 assert(_end >= _top, "Negative buffer");
122 return pointer_delta(_end, _top, HeapWordSize);
123 }
124
125 bool contains(void* addr) {
126 return (void*)_bottom <= addr && addr < (void*)_hard_end;
127 }
128
129 // Sets the space of the buffer to be [buf, space+word_sz()).
130 virtual void set_buf(HeapWord* buf) {
131 _bottom = buf;
132 _top = _bottom;
133 _hard_end = _bottom + word_sz();
134 _end = _hard_end - AlignmentReserve;
135 assert(_end >= _top, "Negative buffer");
136 // In support of ergonomic sizing
137 _allocated += word_sz();
138 }
139
140 // Flush allocation statistics into the given PLABStats supporting ergonomic
141 // sizing of PLAB's and retire the current buffer. To be called at the end of
142 // GC.
143 virtual void flush_and_retire_stats(PLABStats* stats);
144
145 // Fills in the unallocated portion of the buffer with a garbage object and updates
146 // statistics. To be called during GC.
147 virtual void retire();
148
149 void print() PRODUCT_RETURN;
150 };
151
152 // PLAB book-keeping.
153 class PLABStats : public CHeapObj<mtGC> {
154 protected:
155 size_t _allocated; // Total allocated
156 size_t _wasted; // of which wasted (internal fragmentation)
157 size_t _undo_wasted; // of which wasted on undo (is not used for calculation of PLAB size)
158 size_t _unused; // Unused in last buffer
159 size_t _desired_net_plab_sz;// Output of filter (below), suitably trimmed and quantized
160 AdaptiveWeightedAverage
161 _filter; // Integrator with decay
162
163 virtual void reset() {
164 _allocated = 0;
165 _wasted = 0;
166 _undo_wasted = 0;
167 _unused = 0;
168 }
169 public:
170 PLABStats(size_t desired_net_plab_sz_, unsigned wt) :
171 _allocated(0),
172 _wasted(0),
173 _undo_wasted(0),
174 _unused(0),
175 _desired_net_plab_sz(desired_net_plab_sz_),
176 _filter(wt)
177 { }
178
179 virtual ~PLABStats() { }
180
181 static const size_t min_size() {
182 return PLAB::min_size();
183 }
184
185 static const size_t max_size() {
186 return PLAB::max_size();
187 }
188
189 // Calculates plab size for current number of gc worker threads.
190 size_t desired_plab_sz(uint no_of_gc_workers);
191
192 // Updates the current desired PLAB size. Computes the new desired PLAB size with one gc worker thread,
193 // updates _desired_plab_sz and clears sensor accumulators.
194 virtual void adjust_desired_plab_sz();
195
196 inline void add_allocated(size_t v);
197
198 inline void add_unused(size_t v);
199
200 inline void add_wasted(size_t v);
201
202 inline void add_undo_wasted(size_t v);
203 };
204
205 #endif // SHARE_VM_GC_SHARED_PLAB_HPP