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