allocationStats.hpp revision 8413:92457dfb91bd 
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24
25#ifndef SHARE_VM_GC_CMS_ALLOCATIONSTATS_HPP
26#define SHARE_VM_GC_CMS_ALLOCATIONSTATS_HPP
27
28#include "gc/shared/gcUtil.hpp"
29#include "memory/allocation.hpp"
30#include "utilities/globalDefinitions.hpp"
31#include "utilities/macros.hpp"
32
33class AllocationStats VALUE_OBJ_CLASS_SPEC {
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    AdaptivePaddedAverage* dummy =
68      new (&_demand_rate_estimate) AdaptivePaddedAverage(CMS_FLSWeight,
69                                                         CMS_FLSPadding);
70    _desired = 0;
71    _coal_desired = 0;
72    _surplus = 0;
73    _bfr_surp = 0;
74    _prev_sweep = 0;
75    _before_sweep = 0;
76    _coal_births = 0;
77    _coal_deaths = 0;
78    _split_births = (split_birth ? 1 : 0);
79    _split_deaths = 0;
80    _returned_bytes = 0;
81  }
82
83  AllocationStats() {
84    initialize();
85  }
86
87  // The rate estimate is in blocks per second.
88  void compute_desired(size_t count,
89                       float inter_sweep_current,
90                       float inter_sweep_estimate,
91                       float intra_sweep_estimate) {
92    // If the latest inter-sweep time is below our granularity
93    // of measurement, we may call in here with
94    // inter_sweep_current == 0. However, even for suitably small
95    // but non-zero inter-sweep durations, we may not trust the accuracy
96    // of accumulated data, since it has not been "integrated"
97    // (read "low-pass-filtered") long enough, and would be
98    // vulnerable to noisy glitches. In such cases, we
99    // ignore the current sample and use currently available
100    // historical estimates.
101    assert(prev_sweep() + split_births() + coal_births()        // "Total Production Stock"
102           >= split_deaths() + coal_deaths() + (ssize_t)count, // "Current stock + depletion"
103           "Conservation Principle");
104    if (inter_sweep_current > _threshold) {
105      ssize_t demand = prev_sweep() - (ssize_t)count + split_births() + coal_births()
106                       - split_deaths() - coal_deaths();
107      assert(demand >= 0,
108             err_msg("Demand (" SSIZE_FORMAT ") should be non-negative for "
109                     PTR_FORMAT " (size=" SIZE_FORMAT ")",
110                     demand, p2i(this), count));
111      // Defensive: adjust for imprecision in event counting
112      if (demand < 0) {
113        demand = 0;
114      }
115      float old_rate = _demand_rate_estimate.padded_average();
116      float rate = ((float)demand)/inter_sweep_current;
117      _demand_rate_estimate.sample(rate);
118      float new_rate = _demand_rate_estimate.padded_average();
119      ssize_t old_desired = _desired;
120      float delta_ise = (CMSExtrapolateSweep ? intra_sweep_estimate : 0.0);
121      _desired = (ssize_t)(new_rate * (inter_sweep_estimate + delta_ise));
122      if (PrintFLSStatistics > 1) {
123        gclog_or_tty->print_cr("demand: " SSIZE_FORMAT ", old_rate: %f, current_rate: %f, "
124                               "new_rate: %f, old_desired: " SSIZE_FORMAT ", new_desired: " SSIZE_FORMAT,
125                                demand, old_rate, rate, new_rate, old_desired, _desired);
126      }
127    }
128  }
129
130  ssize_t desired() const { return _desired; }
131  void set_desired(ssize_t v) { _desired = v; }
132
133  ssize_t coal_desired() const { return _coal_desired; }
134  void set_coal_desired(ssize_t v) { _coal_desired = v; }
135
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--; }
140
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; }
147
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++; }
151
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++; }
155
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++; }
159
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++; }
163
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};
169
170#endif // SHARE_VM_GC_CMS_ALLOCATIONSTATS_HPP
171