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