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/parGCAllocBuffer.hpp"
27 #include "memory/threadLocalAllocBuffer.hpp"
28 #include "oops/arrayOop.hpp"
29 #include "oops/oop.inline.hpp"
30
31 const size_t ParGCAllocBuffer::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 const size_t ParGCAllocBuffer::max_size() {
37 return ThreadLocalAllocBuffer::max_size();
38 }
39
40 ParGCAllocBuffer::ParGCAllocBuffer(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)
43 {
44 assert (min_size() > AlignmentReserve, "Inconsistency!");
45 // ArrayOopDesc::header_size depends on command line initialization.
46 AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? align_object_size(arrayOopDesc::header_size(T_INT)) : 0;
47 }
48
49 // If the minimum object size is greater than MinObjAlignment, we can
50 // end up with a shard at the end of the buffer that's smaller than
51 // the smallest object. We can't allow that because the buffer must
52 // look like it's full of objects when we retire it, so we make
53 // sure we have enough space for a filler int array object.
54 size_t ParGCAllocBuffer::AlignmentReserve;
55
56 void ParGCAllocBuffer::flush_and_retire_stats(PLABStats* stats) {
57 // We want to distinguish between unused space in the last buffer and waste
58 // created otherwise. Save the amount of unused space because retire() will
59 // update the pointers we use.
60 size_t unused = pointer_delta(_end, _top);
61
62 // Retire the last allocation buffer.
63 retire();
64
65 stats->add_allocated(_allocated);
66 // Retire() counts the unused space as wasted. So we need to remove it again
67 // before updating the statistics.
68 stats->add_wasted(_wasted - unused);
69 stats->add_unused(unused);
70
71 // Since we have flushed the stats we need to clear the _allocated and _wasted
72 // fields in case somebody retains an instance of this over GCs. Not doing so
73 // will artifically inflate the values in the statistics.
74 _allocated = 0;
75 _wasted = 0;
76 }
77
78 void ParGCAllocBuffer::retire() {
79 if (_top < _hard_end) {
80 CollectedHeap::fill_with_object(_top, _hard_end);
81 invalidate();
82 }
83 }
84
85 // Compute desired plab size and latch result for later
86 // use. This should be called once at the end of parallel
87 // scavenge; it clears the sensor accumulators.
88 void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) {
89 assert(ResizePLAB, "Not set");
90
91 assert(is_object_aligned(max_size()) && min_size() <= max_size(),
92 "PLAB clipping computation may be incorrect");
93
94 if (_allocated == 0) {
95 assert(_unused == 0,
96 err_msg("Inconsistency in PLAB stats: "
97 "_allocated: "SIZE_FORMAT", "
98 "_wasted: "SIZE_FORMAT", "
99 "_unused: "SIZE_FORMAT,
100 _allocated, _wasted, _unused));
101
102 _allocated = 1;
103 }
104 double wasted_frac = (double)_unused / (double)_allocated;
105 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct);
106 if (target_refills == 0) {
107 target_refills = 1;
108 }
109 size_t used = _allocated - _wasted - _unused;
110 size_t recent_plab_sz = used / (target_refills * no_of_gc_workers);
111 // Take historical weighted average
112 _filter.sample(recent_plab_sz);
113 // Clip from above and below, and align to object boundary
114 size_t new_plab_sz = MAX2(min_size(), (size_t)_filter.average());
115 new_plab_sz = MIN2(max_size(), new_plab_sz);
116 new_plab_sz = align_object_size(new_plab_sz);
117 // Latch the result
118 if (PrintPLAB) {
119 gclog_or_tty->print(" (plab_sz = " SIZE_FORMAT" desired_plab_sz = " SIZE_FORMAT") ", recent_plab_sz, new_plab_sz);
120 }
121 _desired_plab_sz = new_plab_sz;
122
123 reset();
124 }
125
126 #ifndef PRODUCT
127 void ParGCAllocBuffer::print() {
128 gclog_or_tty->print_cr("parGCAllocBuffer: _bottom: " PTR_FORMAT " _top: " PTR_FORMAT
129 " _end: " PTR_FORMAT " _hard_end: " PTR_FORMAT ")",
130 p2i(_bottom), p2i(_top), p2i(_end), p2i(_hard_end));
131 }
132 #endif // !PRODUCT