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