1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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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 
  33 class 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