Mon, 06 Aug 2012 12:20:14 -0700
6818524: G1: use ergonomic resizing of PLABs
Summary: Employ PLABStats instances to record information about survivor and old PLABs, and use the recorded stats to adjust the sizes of survivor and old PLABS.
Reviewed-by: johnc, ysr
Contributed-by: Brandon Mitchell <brandon@twitter.com>
1 /*
2 * Copyright (c) 2001, 2011, 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 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_SHARED_ALLOCATIONSTATS_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_SHARED_ALLOCATIONSTATS_HPP
28 #ifndef SERIALGC
29 #include "gc_implementation/shared/gcUtil.hpp"
30 #include "memory/allocation.hpp"
31 #include "utilities/globalDefinitions.hpp"
32 #endif
34 class AllocationStats VALUE_OBJ_CLASS_SPEC {
35 // A duration threshold (in ms) used to filter
36 // possibly unreliable samples.
37 static float _threshold;
39 // We measure the demand between the end of the previous sweep and
40 // beginning of this sweep:
41 // Count(end_last_sweep) - Count(start_this_sweep)
42 // + split_births(between) - split_deaths(between)
43 // The above number divided by the time since the end of the
44 // previous sweep gives us a time rate of demand for blocks
45 // of this size. We compute a padded average of this rate as
46 // our current estimate for the time rate of demand for blocks
47 // of this size. Similarly, we keep a padded average for the time
48 // between sweeps. Our current estimate for demand for blocks of
49 // this size is then simply computed as the product of these two
50 // estimates.
51 AdaptivePaddedAverage _demand_rate_estimate;
53 ssize_t _desired; // Demand stimate computed as described above
54 ssize_t _coal_desired; // desired +/- small-percent for tuning coalescing
56 ssize_t _surplus; // count - (desired +/- small-percent),
57 // used to tune splitting in best fit
58 ssize_t _bfr_surp; // surplus at start of current sweep
59 ssize_t _prev_sweep; // count from end of previous sweep
60 ssize_t _before_sweep; // count from before current sweep
61 ssize_t _coal_births; // additional chunks from coalescing
62 ssize_t _coal_deaths; // loss from coalescing
63 ssize_t _split_births; // additional chunks from splitting
64 ssize_t _split_deaths; // loss from splitting
65 size_t _returned_bytes; // number of bytes returned to list.
66 public:
67 void initialize(bool split_birth = false) {
68 AdaptivePaddedAverage* dummy =
69 new (&_demand_rate_estimate) AdaptivePaddedAverage(CMS_FLSWeight,
70 CMS_FLSPadding);
71 _desired = 0;
72 _coal_desired = 0;
73 _surplus = 0;
74 _bfr_surp = 0;
75 _prev_sweep = 0;
76 _before_sweep = 0;
77 _coal_births = 0;
78 _coal_deaths = 0;
79 _split_births = (split_birth ? 1 : 0);
80 _split_deaths = 0;
81 _returned_bytes = 0;
82 }
84 AllocationStats() {
85 initialize();
86 }
88 // The rate estimate is in blocks per second.
89 void compute_desired(size_t count,
90 float inter_sweep_current,
91 float inter_sweep_estimate,
92 float intra_sweep_estimate) {
93 // If the latest inter-sweep time is below our granularity
94 // of measurement, we may call in here with
95 // inter_sweep_current == 0. However, even for suitably small
96 // but non-zero inter-sweep durations, we may not trust the accuracy
97 // of accumulated data, since it has not been "integrated"
98 // (read "low-pass-filtered") long enough, and would be
99 // vulnerable to noisy glitches. In such cases, we
100 // ignore the current sample and use currently available
101 // historical estimates.
102 assert(prev_sweep() + split_births() + coal_births() // "Total Production Stock"
103 >= split_deaths() + coal_deaths() + (ssize_t)count, // "Current stock + depletion"
104 "Conservation Principle");
105 if (inter_sweep_current > _threshold) {
106 ssize_t demand = prev_sweep() - (ssize_t)count + split_births() + coal_births()
107 - split_deaths() - coal_deaths();
108 assert(demand >= 0,
109 err_msg("Demand (" SSIZE_FORMAT ") should be non-negative for "
110 PTR_FORMAT " (size=" SIZE_FORMAT ")",
111 demand, this, count));
112 // Defensive: adjust for imprecision in event counting
113 if (demand < 0) {
114 demand = 0;
115 }
116 float old_rate = _demand_rate_estimate.padded_average();
117 float rate = ((float)demand)/inter_sweep_current;
118 _demand_rate_estimate.sample(rate);
119 float new_rate = _demand_rate_estimate.padded_average();
120 ssize_t old_desired = _desired;
121 float delta_ise = (CMSExtrapolateSweep ? intra_sweep_estimate : 0.0);
122 _desired = (ssize_t)(new_rate * (inter_sweep_estimate + delta_ise));
123 if (PrintFLSStatistics > 1) {
124 gclog_or_tty->print_cr("demand: %d, old_rate: %f, current_rate: %f, new_rate: %f, old_desired: %d, new_desired: %d",
125 demand, old_rate, rate, new_rate, old_desired, _desired);
126 }
127 }
128 }
130 ssize_t desired() const { return _desired; }
131 void set_desired(ssize_t v) { _desired = v; }
133 ssize_t coal_desired() const { return _coal_desired; }
134 void set_coal_desired(ssize_t v) { _coal_desired = v; }
136 ssize_t surplus() const { return _surplus; }
137 void set_surplus(ssize_t v) { _surplus = v; }
138 void increment_surplus() { _surplus++; }
139 void decrement_surplus() { _surplus--; }
141 ssize_t bfr_surp() const { return _bfr_surp; }
142 void set_bfr_surp(ssize_t v) { _bfr_surp = v; }
143 ssize_t prev_sweep() const { return _prev_sweep; }
144 void set_prev_sweep(ssize_t v) { _prev_sweep = v; }
145 ssize_t before_sweep() const { return _before_sweep; }
146 void set_before_sweep(ssize_t v) { _before_sweep = v; }
148 ssize_t coal_births() const { return _coal_births; }
149 void set_coal_births(ssize_t v) { _coal_births = v; }
150 void increment_coal_births() { _coal_births++; }
152 ssize_t coal_deaths() const { return _coal_deaths; }
153 void set_coal_deaths(ssize_t v) { _coal_deaths = v; }
154 void increment_coal_deaths() { _coal_deaths++; }
156 ssize_t split_births() const { return _split_births; }
157 void set_split_births(ssize_t v) { _split_births = v; }
158 void increment_split_births() { _split_births++; }
160 ssize_t split_deaths() const { return _split_deaths; }
161 void set_split_deaths(ssize_t v) { _split_deaths = v; }
162 void increment_split_deaths() { _split_deaths++; }
164 NOT_PRODUCT(
165 size_t returned_bytes() const { return _returned_bytes; }
166 void set_returned_bytes(size_t v) { _returned_bytes = v; }
167 )
168 };
170 #endif // SHARE_VM_GC_IMPLEMENTATION_SHARED_ALLOCATIONSTATS_HPP