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.
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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_VM_GC_SHARED_PLAB_HPP
26 #define SHARE_VM_GC_SHARED_PLAB_HPP
27
28 #include "gc/shared/gcUtil.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "runtime/atomic.inline.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
68 // Undo the last allocation in the buffer, which is required to be of the
69 // "obj" of the given "word_sz".
70 void undo_last_allocation(HeapWord* obj, size_t word_sz);
71
72 public:
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 virtual ~PLAB() {}
77
78 // Minimum PLAB size.
79 static size_t min_size();
80 // Maximum PLAB size.
81 static size_t max_size();
82
83 // If an allocation of the given "word_sz" can be satisfied within the
84 // buffer, do the allocation, returning a pointer to the start of the
85 // allocated block. If the allocation request cannot be satisfied,
86 // return NULL.
87 HeapWord* allocate(size_t word_sz) {
88 HeapWord* res = _top;
89 if (pointer_delta(_end, _top) >= word_sz) {
90 _top = _top + word_sz;
91 return res;
92 } else {
93 return NULL;
94 }
95 }
96
97 // Allocate the object aligned to "alignment_in_bytes".
98 HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);
99
100 // Undo any allocation in the buffer, which is required to be of the
101 // "obj" of the given "word_sz".
102 void undo_allocation(HeapWord* obj, size_t word_sz);
103
104 // The total (word) size of the buffer, including both allocated and
105 // unallocated space.
106 size_t word_sz() { return _word_sz; }
107
108 size_t waste() { return _wasted; }
109 size_t undo_waste() { return _undo_wasted; }
110
111 // Should only be done if we are about to reset with a new buffer of the
112 // given size.
113 void set_word_size(size_t new_word_sz) {
114 assert(new_word_sz > AlignmentReserve, "Too small");
115 _word_sz = new_word_sz;
116 }
117
118 // The number of words of unallocated space remaining in the buffer.
119 size_t words_remaining() {
120 assert(_end >= _top, "Negative buffer");
121 return pointer_delta(_end, _top, HeapWordSize);
122 }
123
124 bool contains(void* addr) {
125 return (void*)_bottom <= addr && addr < (void*)_hard_end;
126 }
127
128 // Sets the space of the buffer to be [buf, space+word_sz()).
129 virtual void set_buf(HeapWord* buf) {
130 _bottom = buf;
131 _top = _bottom;
132 _hard_end = _bottom + word_sz();
133 _end = _hard_end - AlignmentReserve;
134 assert(_end >= _top, "Negative buffer");
135 // In support of ergonomic sizing
136 _allocated += word_sz();
137 }
138
139 // Flush allocation statistics into the given PLABStats supporting ergonomic
140 // sizing of PLAB's and retire the current buffer. To be called at the end of
141 // GC.
142 virtual void flush_and_retire_stats(PLABStats* stats);
143
144 // Fills in the unallocated portion of the buffer with a garbage object and updates
145 // statistics. To be called during GC.
146 virtual void retire();
147
148 void print() PRODUCT_RETURN;
149 };
150
151 // PLAB book-keeping.
152 class PLABStats : public CHeapObj<mtGC> {
153 protected:
154 size_t _allocated; // Total allocated
155 size_t _wasted; // of which wasted (internal fragmentation)
156 size_t _undo_wasted; // of which wasted on undo (is not used for calculation of PLAB size)
157 size_t _unused; // Unused in last buffer
158 size_t _desired_net_plab_sz;// Output of filter (below), suitably trimmed and quantized
159 AdaptiveWeightedAverage
160 _filter; // Integrator with decay
161
162 virtual void reset() {
163 _allocated = 0;
164 _wasted = 0;
165 _undo_wasted = 0;
166 _unused = 0;
167 }
168 public:
169 PLABStats(size_t desired_net_plab_sz_, unsigned wt) :
170 _allocated(0),
171 _wasted(0),
172 _undo_wasted(0),
173 _unused(0),
174 _desired_net_plab_sz(desired_net_plab_sz_),
175 _filter(wt)
176 { }
177
178 virtual ~PLABStats() { }
179
180 static const size_t min_size() {
181 return PLAB::min_size();
182 }
183
184 static const size_t max_size() {
185 return PLAB::max_size();
186 }
187
188 // Calculates plab size for current number of gc worker threads.
189 size_t desired_plab_sz(uint no_of_gc_workers);
190
191 // Updates the current desired PLAB size. Computes the new desired PLAB size with one gc worker thread,
192 // updates _desired_plab_sz and clears sensor accumulators.
193 virtual void adjust_desired_plab_sz();
194
195 void add_allocated(size_t v) {
196 Atomic::add_ptr(v, &_allocated);
197 }
198
199 void add_unused(size_t v) {
200 Atomic::add_ptr(v, &_unused);
201 }
202
203 void add_wasted(size_t v) {
204 Atomic::add_ptr(v, &_wasted);
205 }
206
207 void add_undo_wasted(size_t v) {
208 Atomic::add_ptr(v, &_undo_wasted);
209 }
210 };
211
212 #endif // SHARE_VM_GC_SHARED_PLAB_HPP