1 /*
2 * Copyright (c) 2001, 2018, 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 #include "precompiled.hpp"
26 #include "gc/shared/collectedHeap.hpp"
27 #include "gc/shared/plab.inline.hpp"
28 #include "gc/shared/threadLocalAllocBuffer.hpp"
29 #include "memory/universe.hpp"
30 #include "logging/log.hpp"
31 #include "oops/arrayOop.hpp"
32 #include "oops/oop.inline.hpp"
33
34 size_t PLAB::min_size() {
35 // Make sure that we return something that is larger than AlignmentReserve
36 return align_object_size(MAX2(MinTLABSize / HeapWordSize, (size_t)oopDesc::header_size())) + AlignmentReserve;
37 }
38
39 size_t PLAB::max_size() {
40 return ThreadLocalAllocBuffer::max_size();
41 }
42
43 PLAB::PLAB(size_t desired_plab_sz_) :
44 _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL),
45 _end(NULL), _hard_end(NULL), _allocated(0), _wasted(0), _undo_wasted(0)
46 {
47 // ArrayOopDesc::header_size depends on command line initialization.
48 CollectedHeap* heap = Universe::heap();
49 int rsv_regular = heap->obj_header_size();
50 int rsv_array = align_object_size(heap->array_header_size(T_INT));
51 AlignmentReserve = rsv_regular > MinObjAlignment ? rsv_array : 0;
52 assert(min_size() > AlignmentReserve,
53 "Minimum PLAB size " SIZE_FORMAT " must be larger than alignment reserve " SIZE_FORMAT " "
54 "to be able to contain objects", min_size(), AlignmentReserve);
55 }
56
57 // If the minimum object size is greater than MinObjAlignment, we can
58 // end up with a shard at the end of the buffer that's smaller than
59 // the smallest object. We can't allow that because the buffer must
60 // look like it's full of objects when we retire it, so we make
61 // sure we have enough space for a filler int array object.
62 size_t PLAB::AlignmentReserve;
63
64 void PLAB::flush_and_retire_stats(PLABStats* stats) {
65 // Retire the last allocation buffer.
66 size_t unused = retire_internal();
67
68 // Now flush the statistics.
69 stats->add_allocated(_allocated);
70 stats->add_wasted(_wasted);
71 stats->add_undo_wasted(_undo_wasted);
72 stats->add_unused(unused);
73
74 // Since we have flushed the stats we need to clear the _allocated and _wasted
75 // fields in case somebody retains an instance of this over GCs. Not doing so
76 // will artifically inflate the values in the statistics.
77 _allocated = 0;
78 _wasted = 0;
79 _undo_wasted = 0;
80 }
81
82 void PLAB::retire() {
83 _wasted += retire_internal();
84 }
85
86 size_t PLAB::retire_internal() {
87 size_t result = 0;
88 if (_top < _hard_end) {
89 assert(pointer_delta(_hard_end, _top) >= (size_t)(Universe::heap()->obj_header_size()),
90 "better have enough space left to fill with dummy");
91 Universe::heap()->fill_with_dummy_object(_top, _hard_end, true);
92 result += invalidate();
93 }
94 return result;
95 }
96
97 void PLAB::add_undo_waste(HeapWord* obj, size_t word_sz) {
98 Universe::heap()->fill_with_dummy_object(obj, obj + word_sz, true);
99 _undo_wasted += word_sz;
100 }
101
102 void PLAB::undo_last_allocation(HeapWord* obj, size_t word_sz) {
103 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
104 assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
105 _top = obj;
106 }
107
108 void PLAB::undo_allocation(HeapWord* obj, size_t word_sz) {
109 // Is the alloc in the current alloc buffer?
110 if (contains(obj)) {
111 assert(contains(obj + word_sz - 1),
112 "should contain whole object");
113 undo_last_allocation(obj, word_sz);
114 } else {
115 add_undo_waste(obj, word_sz);
116 }
117 }
118
119 void PLABStats::log_plab_allocation() {
120 log_debug(gc, plab)("%s PLAB allocation: "
121 "allocated: " SIZE_FORMAT "B, "
122 "wasted: " SIZE_FORMAT "B, "
123 "unused: " SIZE_FORMAT "B, "
124 "used: " SIZE_FORMAT "B, "
125 "undo waste: " SIZE_FORMAT "B, ",
126 _description,
127 _allocated * HeapWordSize,
128 _wasted * HeapWordSize,
129 _unused * HeapWordSize,
130 used() * HeapWordSize,
131 _undo_wasted * HeapWordSize);
132 }
133
134 void PLABStats::log_sizing(size_t calculated_words, size_t net_desired_words) {
135 log_debug(gc, plab)("%s sizing: "
136 "calculated: " SIZE_FORMAT "B, "
137 "actual: " SIZE_FORMAT "B",
138 _description,
139 calculated_words * HeapWordSize,
140 net_desired_words * HeapWordSize);
141 }
142
143 // Calculates plab size for current number of gc worker threads.
144 size_t PLABStats::desired_plab_sz(uint no_of_gc_workers) {
145 return align_object_size(MIN2(MAX2(min_size(), _desired_net_plab_sz / no_of_gc_workers), max_size()));
146 }
147
148 // Compute desired plab size for one gc worker thread and latch result for later
149 // use. This should be called once at the end of parallel
150 // scavenge; it clears the sensor accumulators.
151 void PLABStats::adjust_desired_plab_sz() {
152 log_plab_allocation();
153
154 if (!ResizePLAB) {
155 // Clear accumulators for next round.
156 reset();
157 return;
158 }
159
160 assert(is_object_aligned(max_size()) && min_size() <= max_size(),
161 "PLAB clipping computation may be incorrect");
162
163 assert(_allocated != 0 || _unused == 0,
164 "Inconsistency in PLAB stats: "
165 "_allocated: " SIZE_FORMAT ", "
166 "_wasted: " SIZE_FORMAT ", "
167 "_unused: " SIZE_FORMAT ", "
168 "_undo_wasted: " SIZE_FORMAT,
169 _allocated, _wasted, _unused, _undo_wasted);
170
171 size_t plab_sz = compute_desired_plab_sz();
172 // Take historical weighted average
173 _filter.sample(plab_sz);
174 _desired_net_plab_sz = MAX2(min_size(), (size_t)_filter.average());
175
176 log_sizing(plab_sz, _desired_net_plab_sz);
177 // Clear accumulators for next round
178 reset();
179 }
180
181 size_t PLABStats::compute_desired_plab_sz() {
182 size_t allocated = MAX2(_allocated, size_t(1));
183 double wasted_frac = (double)_unused / (double)allocated;
184 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct);
185 if (target_refills == 0) {
186 target_refills = 1;
187 }
188 size_t used = allocated - _wasted - _unused;
189 // Assumed to have 1 gc worker thread
190 size_t recent_plab_sz = used / target_refills;
191 return recent_plab_sz;
192 }