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.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_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 ParGCAllocBuffer: 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 public:
67 // Initializes the buffer to be empty, but with the given "word_sz".
68 // Must get initialized with "set_buf" for an allocation to succeed.
69 ParGCAllocBuffer(size_t word_sz);
70 virtual ~ParGCAllocBuffer() {}
71
72 // Minimum PLAB size.
73 static size_t min_size();
74 // Maximum PLAB size.
75 static size_t max_size();
76
77 // If an allocation of the given "word_sz" can be satisfied within the
78 // buffer, do the allocation, returning a pointer to the start of the
79 // allocated block. If the allocation request cannot be satisfied,
80 // return NULL.
81 HeapWord* allocate(size_t word_sz) {
82 HeapWord* res = _top;
83 if (pointer_delta(_end, _top) >= word_sz) {
84 _top = _top + word_sz;
85 return res;
86 } else {
87 return NULL;
88 }
89 }
90
91 // Allocate the object aligned to "alignment_in_bytes".
92 HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);
93
94 // Undo the last allocation in the buffer, which is required to be of the
95 // "obj" of the given "word_sz".
96 void undo_allocation(HeapWord* obj, size_t word_sz) {
97 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
98 assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
99 _top = obj;
100 }
101
102 void add_undo_waste(size_t word_sz) {
103 _undo_wasted += word_sz;
104 }
105
106 // The total (word) size of the buffer, including both allocated and
107 // unallocated space.
108 size_t word_sz() { return _word_sz; }
109
110 size_t wasted() { return _wasted; }
111 size_t undo_wasted() { return _undo_wasted; }
112
113 // Should only be done if we are about to reset with a new buffer of the
114 // given size.
115 void set_word_size(size_t new_word_sz) {
116 assert(new_word_sz > AlignmentReserve, "Too small");
117 _word_sz = new_word_sz;
118 }
119
120 // The number of words of unallocated space remaining in the buffer.
121 size_t words_remaining() {
122 assert(_end >= _top, "Negative buffer");
123 return pointer_delta(_end, _top, HeapWordSize);
124 }
125
126 bool contains(void* addr) {
127 return (void*)_bottom <= addr && addr < (void*)_hard_end;
128 }
129
130 // Sets the space of the buffer to be [buf, space+word_sz()).
131 virtual void set_buf(HeapWord* buf) {
132 _bottom = buf;
133 _top = _bottom;
134 _hard_end = _bottom + word_sz();
135 _end = _hard_end - AlignmentReserve;
136 assert(_end >= _top, "Negative buffer");
137 // In support of ergonomic sizing
138 _allocated += word_sz();
139 }
140
141 // Flush allocation statistics into the given PLABStats supporting ergonomic
142 // sizing of PLAB's and retire the current buffer. To be called at the end of
143 // GC.
144 void flush_and_retire_stats(PLABStats* stats);
145
146 // Fills in the unallocated portion of the buffer with a garbage object and updates
147 // statistics. To be called during GC.
148 virtual void retire();
149
150 void print() PRODUCT_RETURN;
151 };
152
153 // PLAB book-keeping.
154 class PLABStats VALUE_OBJ_CLASS_SPEC {
155 size_t _allocated; // Total allocated
156 size_t _wasted; // of which wasted (internal fragmentation)
157 size_t _unused; // Unused in last buffer
158 size_t _desired_plab_sz;// Output of filter (below), suitably trimmed and quantized
159 AdaptiveWeightedAverage
160 _filter; // Integrator with decay
161
162 void reset() {
163 _allocated = 0;
164 _wasted = 0;
165 _unused = 0;
166 }
167 public:
168 PLABStats(size_t desired_plab_sz_, unsigned wt) :
169 _allocated(0),
170 _wasted(0),
171 _unused(0),
172 _desired_plab_sz(desired_plab_sz_),
173 _filter(wt)
174 { }
175
176 static const size_t min_size() {
177 return ParGCAllocBuffer::min_size();
178 }
179
180 static const size_t max_size() {
181 return ParGCAllocBuffer::max_size();
182 }
183
184 size_t desired_plab_sz() {
185 return _desired_plab_sz;
186 }
187
188 // Updates the current desired PLAB size. Computes the new desired PLAB size,
189 // updates _desired_plab_sz and clears sensor accumulators.
190 void adjust_desired_plab_sz(uint no_of_gc_workers);
191
192 void add_allocated(size_t v) {
193 Atomic::add_ptr(v, &_allocated);
194 }
195
196 void add_unused(size_t v) {
197 Atomic::add_ptr(v, &_unused);
198 }
199
200 void add_wasted(size_t v) {
201 Atomic::add_ptr(v, &_wasted);
202 }
203 };
204
205 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP