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.
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_implementation/shared/plab.hpp"
27 #include "memory/threadLocalAllocBuffer.hpp"
28 #include "oops/arrayOop.hpp"
29 #include "oops/oop.inline.hpp"
30
31 size_t PLAB::min_size() {
32 // Make sure that we return something that is larger than AlignmentReserve
33 return align_object_size(MAX2(MinTLABSize / HeapWordSize, (uintx)oopDesc::header_size())) + AlignmentReserve;
34 }
35
36 size_t PLAB::max_size() {
37 return ThreadLocalAllocBuffer::max_size();
38 }
39
40 PLAB::PLAB(size_t desired_plab_sz_) :
41 _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL),
42 _end(NULL), _hard_end(NULL), _allocated(0), _wasted(0), _undo_wasted(0)
43 {
44 // ArrayOopDesc::header_size depends on command line initialization.
45 AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? align_object_size(arrayOopDesc::header_size(T_INT)) : 0;
46 assert(min_size() > AlignmentReserve,
47 err_msg("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 CollectedHeap::fill_with_object(_top, _hard_end);
84 result += invalidate();
85 }
86 return result;
87 }
88
89 // Compute desired plab size and latch result for later
90 // use. This should be called once at the end of parallel
91 // scavenge; it clears the sensor accumulators.
92 void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) {
93 assert(ResizePLAB, "Not set");
94
95 assert(is_object_aligned(max_size()) && min_size() <= max_size(),
96 "PLAB clipping computation may be incorrect");
97
98 if (_allocated == 0) {
99 assert(_unused == 0,
100 err_msg("Inconsistency in PLAB stats: "
101 "_allocated: "SIZE_FORMAT", "
102 "_wasted: "SIZE_FORMAT", "
103 "_unused: "SIZE_FORMAT", ",
104 "_undo_wasted: "SIZE_FORMAT,
105 _allocated, _wasted, _unused, _undo_wasted));
106
107 _allocated = 1;
108 }
109 double wasted_frac = (double)_unused / (double)_allocated;
110 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct);
111 if (target_refills == 0) {
112 target_refills = 1;
113 }
114 size_t used = _allocated - _wasted - _unused;
115 size_t recent_plab_sz = used / (target_refills * no_of_gc_workers);
116 // Take historical weighted average
117 _filter.sample(recent_plab_sz);
118 // Clip from above and below, and align to object boundary
119 size_t new_plab_sz = MAX2(min_size(), (size_t)_filter.average());
120 new_plab_sz = MIN2(max_size(), new_plab_sz);
121 new_plab_sz = align_object_size(new_plab_sz);
122 // Latch the result
123 if (PrintPLAB) {
124 gclog_or_tty->print(" (plab_sz = " SIZE_FORMAT" desired_plab_sz = " SIZE_FORMAT") ", recent_plab_sz, new_plab_sz);
125 }
126 _desired_plab_sz = new_plab_sz;
127
128 reset();
129 }
130
131 #ifndef PRODUCT
132 void PLAB::print() {
133 gclog_or_tty->print_cr("PLAB: _bottom: " PTR_FORMAT " _top: " PTR_FORMAT
134 " _end: " PTR_FORMAT " _hard_end: " PTR_FORMAT ")",
135 p2i(_bottom), p2i(_top), p2i(_end), p2i(_hard_end));
136 }
137 #endif // !PRODUCT