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.
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_SHARED_PLAB_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_SHARED_PLAB_HPP
27
28 #include "gc_implementation/shared/gcUtil.hpp"
29 #include "memory/allocation.hpp"
30 #include "runtime/atomic.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 // Forward declarations.
34 class PLABStats;
35
36 // A per-thread allocation buffer used during GC.
37 class PLAB: public CHeapObj<mtGC> {
38 protected:
39 char head[32];
40 size_t _word_sz; // In HeapWord units
41 HeapWord* _bottom;
42 HeapWord* _top;
43 HeapWord* _end; // Last allocatable address + 1
44 HeapWord* _hard_end; // _end + AlignmentReserve
45 // In support of ergonomic sizing of PLAB's
46 size_t _allocated; // in HeapWord units
47 size_t _wasted; // in HeapWord units
48 size_t _undo_wasted;
49 char tail[32];
50 static size_t AlignmentReserve;
51
52 // Force future allocations to fail and queries for contains()
53 // to return false. Returns the amount of unused space in this PLAB.
54 size_t invalidate() {
55 _end = _hard_end;
56 size_t remaining = pointer_delta(_end, _top); // Calculate remaining space.
57 _top = _end; // Force future allocations to fail.
58 _bottom = _end; // Force future contains() queries to return false.
59 return remaining;
60 }
61
62 // Fill in remaining space with a dummy object and invalidate the PLAB. Returns
63 // the amount of remaining space.
64 size_t retire_internal();
65
66 void add_undo_waste(HeapWord* obj, size_t word_sz) {
67 CollectedHeap::fill_with_object(obj, word_sz);
68 _undo_wasted += word_sz;
69 }
70
71 // Undo the last allocation in the buffer, which is required to be of the
72 // "obj" of the given "word_sz".
73 void undo_last_allocation(HeapWord* obj, size_t word_sz) {
74 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
75 assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
76 _top = obj;
77 }
78
79 public:
80 // Initializes the buffer to be empty, but with the given "word_sz".
81 // Must get initialized with "set_buf" for an allocation to succeed.
82 PLAB(size_t word_sz);
83 virtual ~PLAB() {}
84
85 // Minimum PLAB size.
86 static size_t min_size();
87 // Maximum PLAB size.
88 static size_t max_size();
89
90 // If an allocation of the given "word_sz" can be satisfied within the
91 // buffer, do the allocation, returning a pointer to the start of the
92 // allocated block. If the allocation request cannot be satisfied,
93 // return NULL.
94 HeapWord* allocate(size_t word_sz) {
95 HeapWord* res = _top;
96 if (pointer_delta(_end, _top) >= word_sz) {
97 _top = _top + word_sz;
98 return res;
99 } else {
100 return NULL;
101 }
102 }
103
104 // Allocate the object aligned to "alignment_in_bytes".
105 HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);
106
107 // Undo any allocation in the buffer, which is required to be of the
108 // "obj" of the given "word_sz".
109 void undo_allocation(HeapWord* obj, size_t word_sz) {
110 // Is the alloc in the current alloc buffer?
111 if (contains(obj)) {
112 assert(contains(obj + word_sz - 1),
113 "should contain whole object");
114 undo_last_allocation(obj, word_sz);
115 } else {
116 add_undo_waste(obj, word_sz);
117 }
118 }
119
120 // The total (word) size of the buffer, including both allocated and
121 // unallocated space.
122 size_t word_sz() { return _word_sz; }
123
124 size_t waste() { return _wasted; }
125 size_t undo_waste() { return _undo_wasted; }
126
127 // Should only be done if we are about to reset with a new buffer of the
128 // given size.
129 void set_word_size(size_t new_word_sz) {
130 assert(new_word_sz > AlignmentReserve, "Too small");
131 _word_sz = new_word_sz;
132 }
133
134 // The number of words of unallocated space remaining in the buffer.
135 size_t words_remaining() {
136 assert(_end >= _top, "Negative buffer");
137 return pointer_delta(_end, _top, HeapWordSize);
138 }
139
140 bool contains(void* addr) {
141 return (void*)_bottom <= addr && addr < (void*)_hard_end;
142 }
143
144 // Sets the space of the buffer to be [buf, space+word_sz()).
145 virtual void set_buf(HeapWord* buf) {
146 _bottom = buf;
147 _top = _bottom;
148 _hard_end = _bottom + word_sz();
149 _end = _hard_end - AlignmentReserve;
150 assert(_end >= _top, "Negative buffer");
151 // In support of ergonomic sizing
152 _allocated += word_sz();
153 }
154
155 // Flush allocation statistics into the given PLABStats supporting ergonomic
156 // sizing of PLAB's and retire the current buffer. To be called at the end of
157 // GC.
158 void flush_and_retire_stats(PLABStats* stats);
159
160 // Fills in the unallocated portion of the buffer with a garbage object and updates
161 // statistics. To be called during GC.
162 virtual void retire();
163
164 void print() PRODUCT_RETURN;
165 };
166
167 // PLAB 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 _undo_wasted; // of which wasted on undo (is not used for calculation of PLAB size)
172 size_t _unused; // Unused in last buffer
173 size_t _desired_plab_sz;// Output of filter (below), suitably trimmed and quantized
174 AdaptiveWeightedAverage
175 _filter; // Integrator with decay
176
177 void reset() {
178 _allocated = 0;
179 _wasted = 0;
180 _undo_wasted = 0;
181 _unused = 0;
182 }
183 public:
184 PLABStats(size_t desired_plab_sz_, unsigned wt) :
185 _allocated(0),
186 _wasted(0),
187 _undo_wasted(0),
188 _unused(0),
189 _desired_plab_sz(desired_plab_sz_),
190 _filter(wt)
191 { }
192
193 static const size_t min_size() {
194 return PLAB::min_size();
195 }
196
197 static const size_t max_size() {
198 return PLAB::max_size();
199 }
200
201 size_t desired_plab_sz() {
202 return _desired_plab_sz;
203 }
204
205 // Updates the current desired PLAB size. Computes the new desired PLAB size,
206 // updates _desired_plab_sz and clears sensor accumulators.
207 void adjust_desired_plab_sz(uint no_of_gc_workers);
208
209 void add_allocated(size_t v) {
210 Atomic::add_ptr(v, &_allocated);
211 }
212
213 void add_unused(size_t v) {
214 Atomic::add_ptr(v, &_unused);
215 }
216
217 void add_wasted(size_t v) {
218 Atomic::add_ptr(v, &_wasted);
219 }
220
221 void add_undo_wasted(size_t v) {
222 Atomic::add_ptr(v, &_undo_wasted);
223 }
224 };
225
226 #endif // SHARE_VM_GC_IMPLEMENTATION_SHARED_PLAB_HPP