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_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 char tail[32];
49 static size_t AlignmentReserve;
50
51 public:
52 // Initializes the buffer to be empty, but with the given "word_sz".
53 // Must get initialized with "set_buf" for an allocation to succeed.
54 ParGCAllocBuffer(size_t word_sz);
55 virtual ~ParGCAllocBuffer() {}
56
57 // Minimum PLAB size.
58 static const size_t min_size();
59 // Maximum PLAB size.
60 static const size_t max_size();
61
62 // If an allocation of the given "word_sz" can be satisfied within the
63 // buffer, do the allocation, returning a pointer to the start of the
64 // allocated block. If the allocation request cannot be satisfied,
65 // return NULL.
66 HeapWord* allocate(size_t word_sz) {
67 HeapWord* res = _top;
68 if (pointer_delta(_end, _top) >= word_sz) {
69 _top = _top + word_sz;
70 return res;
71 } else {
72 return NULL;
73 }
74 }
75
76 // Allocate the object aligned to "alignment_in_bytes".
77 HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);
78
79 // Undo the last allocation in the buffer, which is required to be of the
80 // "obj" of the given "word_sz".
81 void undo_allocation(HeapWord* obj, size_t word_sz) {
82 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
83 assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
84 _top = obj;
85 }
86
87 // The total (word) size of the buffer, including both allocated and
88 // unallocated space.
89 size_t word_sz() { return _word_sz; }
90
91 // Should only be done if we are about to reset with a new buffer of the
92 // given size.
93 void set_word_size(size_t new_word_sz) {
94 assert(new_word_sz > AlignmentReserve, "Too small");
95 _word_sz = new_word_sz;
96 }
97
98 // The number of words of unallocated space remaining in the buffer.
99 size_t words_remaining() {
100 assert(_end >= _top, "Negative buffer");
101 return pointer_delta(_end, _top, HeapWordSize);
102 }
103
104 bool contains(void* addr) {
105 return (void*)_bottom <= addr && addr < (void*)_hard_end;
106 }
107
108 // Sets the space of the buffer to be [buf, space+word_sz()).
109 virtual void set_buf(HeapWord* buf) {
110 _bottom = buf;
111 _top = _bottom;
112 _hard_end = _bottom + word_sz();
113 _end = _hard_end - AlignmentReserve;
114 assert(_end >= _top, "Negative buffer");
115 // In support of ergonomic sizing
116 _allocated += word_sz();
117 }
118
119 // Flush allocation statistics into the given PLABStats supporting ergonomic
120 // sizing of PLAB's and retire the current buffer.
121 void flush_and_retire_stats(PLABStats* stats);
122
123 // Force future allocations to fail and queries for contains()
124 // to return false
125 void invalidate() {
126 _end = _hard_end;
127 _wasted += pointer_delta(_end, _top); // unused space
128 _top = _end; // force future allocations to fail
129 _bottom = _end; // force future contains() queries to return false
130 }
131
132 // Fills in the unallocated portion of the buffer with a garbage object and update
133 // statistics.
134 virtual void retire();
135
136 void print() PRODUCT_RETURN;
137 };
138
139 // PLAB book-keeping.
140 class PLABStats VALUE_OBJ_CLASS_SPEC {
141 size_t _allocated; // Total allocated
142 size_t _wasted; // of which wasted (internal fragmentation)
143 size_t _unused; // Unused in last buffer
144 size_t _desired_plab_sz;// Output of filter (below), suitably trimmed and quantized
145 AdaptiveWeightedAverage
146 _filter; // Integrator with decay
147
148 void reset() {
149 _allocated = 0;
150 _wasted = 0;
151 _unused = 0;
152 }
153 public:
154 PLABStats(size_t desired_plab_sz_, unsigned wt) :
155 _allocated(0),
156 _wasted(0),
157 _unused(0),
158 _desired_plab_sz(desired_plab_sz_),
159 _filter(wt)
160 { }
161
162 static const size_t min_size() {
163 return ParGCAllocBuffer::min_size();
164 }
165
166 static const size_t max_size() {
167 return ParGCAllocBuffer::max_size();
168 }
169
170 size_t desired_plab_sz() {
171 return _desired_plab_sz;
172 }
173
174 // Updates the current desired PLAB size. Computes the new desired PLAB size,
175 // updates _desired_plab_sz and clears sensor accumulators.
176 void adjust_desired_plab_sz(uint no_of_gc_workers);
177
178 void add_allocated(size_t v) {
179 Atomic::add_ptr(v, &_allocated);
180 }
181
182 void add_unused(size_t v) {
183 Atomic::add_ptr(v, &_unused);
184 }
185
186 void add_wasted(size_t v) {
187 Atomic::add_ptr(v, &_wasted);
188 }
189 };
190
191 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP