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