1 /*
2 * Copyright (c) 2001, 2023, 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_GC_SHARED_PLAB_HPP
26 #define SHARE_GC_SHARED_PLAB_HPP
27
28 #include "gc/shared/collectedHeap.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
50 // Force future allocations to fail and queries for contains()
51 // to return false. Returns the amount of unused space in this PLAB.
52 size_t invalidate() {
53 _end = _hard_end;
54 size_t remaining = pointer_delta(_end, _top); // Calculate remaining space.
55 _top = _end; // Force future allocations to fail.
56 _bottom = _end; // Force future contains() queries to return false.
57 return remaining;
58 }
59
60 // Fill in remaining space with a dummy object and invalidate the PLAB. Returns
61 // the amount of remaining space.
62 size_t retire_internal();
63
64 void add_undo_waste(HeapWord* obj, size_t word_sz);
65
66 // Undo the last allocation in the buffer, which is required to be of the
67 // "obj" of the given "word_sz".
68 void undo_last_allocation(HeapWord* obj, size_t word_sz);
69
70 public:
71 static void startup_initialization();
72
73 // Initializes the buffer to be empty, but with the given "word_sz".
74 // Must get initialized with "set_buf" for an allocation to succeed.
75 PLAB(size_t word_sz);
76
77 static size_t size_required_for_allocation(size_t word_size) { return word_size + CollectedHeap::lab_alignment_reserve(); }
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 nullptr;
95 }
96 }
97
98 // Undo any allocation in the buffer, which is required to be of the
99 // "obj" of the given "word_sz".
100 void undo_allocation(HeapWord* obj, size_t word_sz);
101
102 // The total (word) size of the buffer, including both allocated and
103 // unallocated space.
104 size_t word_sz() { return _word_sz; }
105
106 size_t waste() { return _wasted; }
107 size_t undo_waste() { return _undo_wasted; }
108
109 // The number of words of unallocated space remaining in the buffer.
110 size_t words_remaining() {
111 assert(_end >= _top, "Negative buffer");
112 return pointer_delta(_end, _top, HeapWordSize);
113 }
114
115 bool contains(void* addr) {
116 return (void*)_bottom <= addr && addr < (void*)_hard_end;
117 }
118
119 // Sets the space of the buffer to be [buf, space+word_sz()).
120 void set_buf(HeapWord* buf, size_t new_word_sz) {
121 assert(new_word_sz > CollectedHeap::lab_alignment_reserve(), "Too small");
122 _word_sz = new_word_sz;
123
124 _bottom = buf;
125 _top = _bottom;
126 _hard_end = _bottom + word_sz();
127 _end = _hard_end - CollectedHeap::lab_alignment_reserve();
128 assert(_end >= _top, "Negative buffer");
129 // In support of ergonomic sizing
130 _allocated += word_sz();
131 }
132
133 // Flush allocation statistics into the given PLABStats supporting ergonomic
134 // sizing of PLAB's and retire the current buffer. To be called at the end of
135 // GC.
136 void flush_and_retire_stats(PLABStats* stats);
137
138 // Fills in the unallocated portion of the buffer with a garbage object and updates
139 // statistics. To be called during GC.
140 void retire();
141 };
142
143 // PLAB book-keeping.
144 class PLABStats : public CHeapObj<mtGC> {
145 protected:
146 const char* _description; // Identifying string.
147
148 size_t _allocated; // Total allocated
149 size_t _wasted; // of which wasted (internal fragmentation)
150 size_t _undo_wasted; // of which wasted on undo (is not used for calculation of PLAB size)
151 size_t _unused; // Unused in last buffer
152
153 virtual void reset() {
154 _allocated = 0;
155 _wasted = 0;
156 _undo_wasted = 0;
157 _unused = 0;
158 }
159
160 public:
161 PLABStats(const char* description) :
162 _description(description),
163 _allocated(0),
164 _wasted(0),
165 _undo_wasted(0),
166 _unused(0)
167 { }
168
169 virtual ~PLABStats() { }
170
171 size_t allocated() const { return _allocated; }
172 size_t wasted() const { return _wasted; }
173 size_t unused() const { return _unused; }
174 size_t used() const { return allocated() - (wasted() + unused()); }
175 size_t undo_wasted() const { return _undo_wasted; }
176
177 static const size_t min_size() {
178 return PLAB::min_size();
179 }
180
181 static const size_t max_size() {
182 return PLAB::max_size();
183 }
184
185 inline void add_allocated(size_t v);
186
187 inline void add_unused(size_t v);
188
189 inline void add_wasted(size_t v);
190
191 inline void add_undo_wasted(size_t v);
192 };
193
194 #endif // SHARE_GC_SHARED_PLAB_HPP