1 /*
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   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.
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   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
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  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
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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 "runtime/globals.hpp"
  31 #include "utilities/globalDefinitions.hpp"
  32 #include "utilities/macros.hpp"
  33 
  34 class AllocationStats {
  35   // A duration threshold (in ms) used to filter
  36   // possibly unreliable samples.
  37   static float _threshold;
  38 
  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;
  52 
  53   ssize_t     _desired;          // Demand estimate computed as described above
  54   ssize_t     _coal_desired;     // desired +/- small-percent for tuning coalescing
  55 
  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 
  69   AllocationStats() {
  70     initialize();
  71   }
  72 
  73   // The rate estimate is in blocks per second.
  74   void compute_desired(size_t count,
  75                        float inter_sweep_current,
  76                        float inter_sweep_estimate,
  77                        float intra_sweep_estimate) {
  78     // If the latest inter-sweep time is below our granularity
  79     // of measurement, we may call in here with
  80     // inter_sweep_current == 0. However, even for suitably small
  81     // but non-zero inter-sweep durations, we may not trust the accuracy
  82     // of accumulated data, since it has not been "integrated"
  83     // (read "low-pass-filtered") long enough, and would be
  84     // vulnerable to noisy glitches. In such cases, we
  85     // ignore the current sample and use currently available
  86     // historical estimates.
  87     assert(prev_sweep() + split_births() + coal_births()        // "Total Production Stock"
  88            >= split_deaths() + coal_deaths() + (ssize_t)count, // "Current stock + depletion"
  89            "Conservation Principle");
  90     if (inter_sweep_current > _threshold) {
  91       ssize_t demand = prev_sweep() - (ssize_t)count + split_births() + coal_births()
  92                        - split_deaths() - coal_deaths();
  93       assert(demand >= 0,
  94              "Demand (" SSIZE_FORMAT ") should be non-negative for "
  95              PTR_FORMAT " (size=" SIZE_FORMAT ")",
  96              demand, p2i(this), count);
  97       // Defensive: adjust for imprecision in event counting
  98       if (demand < 0) {
  99         demand = 0;
 100       }
 101       float old_rate = _demand_rate_estimate.padded_average();
 102       float rate = ((float)demand)/inter_sweep_current;
 103       _demand_rate_estimate.sample(rate);
 104       float new_rate = _demand_rate_estimate.padded_average();
 105       ssize_t old_desired = _desired;
 106       float delta_ise = (CMSExtrapolateSweep ? intra_sweep_estimate : 0.0);
 107       _desired = (ssize_t)(new_rate * (inter_sweep_estimate + delta_ise));
 108       log_trace(gc, freelist)("demand: " SSIZE_FORMAT ", old_rate: %f, current_rate: %f, "
 109                               "new_rate: %f, old_desired: " SSIZE_FORMAT ", new_desired: " SSIZE_FORMAT,
 110                               demand, old_rate, rate, new_rate, old_desired, _desired);
 111     }
 112   }
 113 
 114   ssize_t desired() const { return _desired; }
 115   void set_desired(ssize_t v) { _desired = v; }
 116 
 117   ssize_t coal_desired() const { return _coal_desired; }
 118   void set_coal_desired(ssize_t v) { _coal_desired = v; }
 119 
 120   ssize_t surplus() const { return _surplus; }
 121   void set_surplus(ssize_t v) { _surplus = v; }
 122   void increment_surplus() { _surplus++; }
 123   void decrement_surplus() { _surplus--; }
 124 
 125   ssize_t bfr_surp() const { return _bfr_surp; }
 126   void set_bfr_surp(ssize_t v) { _bfr_surp = v; }
 127   ssize_t prev_sweep() const { return _prev_sweep; }
 128   void set_prev_sweep(ssize_t v) { _prev_sweep = v; }
 129   ssize_t before_sweep() const { return _before_sweep; }
 130   void set_before_sweep(ssize_t v) { _before_sweep = v; }
 131 
 132   ssize_t coal_births() const { return _coal_births; }
 133   void set_coal_births(ssize_t v) { _coal_births = v; }
 134   void increment_coal_births() { _coal_births++; }
 135 
 136   ssize_t coal_deaths() const { return _coal_deaths; }
 137   void set_coal_deaths(ssize_t v) { _coal_deaths = v; }
 138   void increment_coal_deaths() { _coal_deaths++; }
 139 
 140   ssize_t split_births() const { return _split_births; }
 141   void set_split_births(ssize_t v) { _split_births = v; }
 142   void increment_split_births() { _split_births++; }
 143 
 144   ssize_t split_deaths() const { return _split_deaths; }
 145   void set_split_deaths(ssize_t v) { _split_deaths = v; }
 146   void increment_split_deaths() { _split_deaths++; }
 147 
 148   NOT_PRODUCT(
 149     size_t returned_bytes() const { return _returned_bytes; }
 150     void set_returned_bytes(size_t v) { _returned_bytes = v; }
 151   )
 152 };
 153 
 154 #endif // SHARE_GC_CMS_ALLOCATIONSTATS_HPP