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24
25#ifndef SHARE_GC_CMS_ALLOCATIONSTATS_HPP
26#define SHARE_GC_CMS_ALLOCATIONSTATS_HPP
27
28#include "gc/shared/gcUtil.hpp"
29#include "logging/log.hpp"
30#include "utilities/globalDefinitions.hpp"
31#include "utilities/macros.hpp"
32
33class AllocationStats {
34 // A duration threshold (in ms) used to filter
35 // possibly unreliable samples.
36 static float _threshold;
37
38 // We measure the demand between the end of the previous sweep and
39 // beginning of this sweep:
40 // Count(end_last_sweep) - Count(start_this_sweep)
41 // + split_births(between) - split_deaths(between)
42 // The above number divided by the time since the end of the
43 // previous sweep gives us a time rate of demand for blocks
44 // of this size. We compute a padded average of this rate as
45 // our current estimate for the time rate of demand for blocks
46 // of this size. Similarly, we keep a padded average for the time
47 // between sweeps. Our current estimate for demand for blocks of
48 // this size is then simply computed as the product of these two
49 // estimates.
50 AdaptivePaddedAverage _demand_rate_estimate;
51
52 ssize_t _desired; // Demand estimate computed as described above
53 ssize_t _coal_desired; // desired +/- small-percent for tuning coalescing
54
55 ssize_t _surplus; // count - (desired +/- small-percent),
56 // used to tune splitting in best fit
57 ssize_t _bfr_surp; // surplus at start of current sweep
58 ssize_t _prev_sweep; // count from end of previous sweep
59 ssize_t _before_sweep; // count from before current sweep
60 ssize_t _coal_births; // additional chunks from coalescing
61 ssize_t _coal_deaths; // loss from coalescing
62 ssize_t _split_births; // additional chunks from splitting
63 ssize_t _split_deaths; // loss from splitting
64 size_t _returned_bytes; // number of bytes returned to list.
65 public:
66 void initialize(bool split_birth = false);
67
68 AllocationStats() {
69 initialize();
70 }
71
72 // The rate estimate is in blocks per second.
73 void compute_desired(size_t count,
74 float inter_sweep_current,
75 float inter_sweep_estimate,
76 float intra_sweep_estimate) {
77 // If the latest inter-sweep time is below our granularity
78 // of measurement, we may call in here with
79 // inter_sweep_current == 0. However, even for suitably small
80 // but non-zero inter-sweep durations, we may not trust the accuracy
81 // of accumulated data, since it has not been "integrated"
82 // (read "low-pass-filtered") long enough, and would be
83 // vulnerable to noisy glitches. In such cases, we
84 // ignore the current sample and use currently available
85 // historical estimates.
86 assert(prev_sweep() + split_births() + coal_births() // "Total Production Stock"
87 >= split_deaths() + coal_deaths() + (ssize_t)count, // "Current stock + depletion"
88 "Conservation Principle");
89 if (inter_sweep_current > _threshold) {
90 ssize_t demand = prev_sweep() - (ssize_t)count + split_births() + coal_births()
91 - split_deaths() - coal_deaths();
92 assert(demand >= 0,
93 "Demand (" SSIZE_FORMAT ") should be non-negative for "
94 PTR_FORMAT " (size=" SIZE_FORMAT ")",
95 demand, p2i(this), count);
96 // Defensive: adjust for imprecision in event counting
97 if (demand < 0) {
98 demand = 0;
99 }
100 float old_rate = _demand_rate_estimate.padded_average();
101 float rate = ((float)demand)/inter_sweep_current;
102 _demand_rate_estimate.sample(rate);
103 float new_rate = _demand_rate_estimate.padded_average();
104 ssize_t old_desired = _desired;
105 float delta_ise = (CMSExtrapolateSweep ? intra_sweep_estimate : 0.0);
106 _desired = (ssize_t)(new_rate * (inter_sweep_estimate + delta_ise));
107 log_trace(gc, freelist)("demand: " SSIZE_FORMAT ", old_rate: %f, current_rate: %f, "
108 "new_rate: %f, old_desired: " SSIZE_FORMAT ", new_desired: " SSIZE_FORMAT,
109 demand, old_rate, rate, new_rate, old_desired, _desired);
110 }
111 }
112
113 ssize_t desired() const { return _desired; }
114 void set_desired(ssize_t v) { _desired = v; }
115
116 ssize_t coal_desired() const { return _coal_desired; }
117 void set_coal_desired(ssize_t v) { _coal_desired = v; }
118
119 ssize_t surplus() const { return _surplus; }
120 void set_surplus(ssize_t v) { _surplus = v; }
121 void increment_surplus() { _surplus++; }
122 void decrement_surplus() { _surplus--; }
123
124 ssize_t bfr_surp() const { return _bfr_surp; }
125 void set_bfr_surp(ssize_t v) { _bfr_surp = v; }
126 ssize_t prev_sweep() const { return _prev_sweep; }
127 void set_prev_sweep(ssize_t v) { _prev_sweep = v; }
128 ssize_t before_sweep() const { return _before_sweep; }
129 void set_before_sweep(ssize_t v) { _before_sweep = v; }
130
131 ssize_t coal_births() const { return _coal_births; }
132 void set_coal_births(ssize_t v) { _coal_births = v; }
133 void increment_coal_births() { _coal_births++; }
134
135 ssize_t coal_deaths() const { return _coal_deaths; }
136 void set_coal_deaths(ssize_t v) { _coal_deaths = v; }
137 void increment_coal_deaths() { _coal_deaths++; }
138
139 ssize_t split_births() const { return _split_births; }
140 void set_split_births(ssize_t v) { _split_births = v; }
141 void increment_split_births() { _split_births++; }
142
143 ssize_t split_deaths() const { return _split_deaths; }
144 void set_split_deaths(ssize_t v) { _split_deaths = v; }
145 void increment_split_deaths() { _split_deaths++; }
146
147 NOT_PRODUCT(
148 size_t returned_bytes() const { return _returned_bytes; }
149 void set_returned_bytes(size_t v) { _returned_bytes = v; }
150 )
151};
152
153#endif // SHARE_GC_CMS_ALLOCATIONSTATS_HPP
154