1 /*
   2  * Copyright 2001-2005 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 class AllocationStats VALUE_OBJ_CLASS_SPEC {
  26   // A duration threshold (in ms) used to filter
  27   // possibly unreliable samples.
  28   static float _threshold;
  29 
  30   // We measure the demand between the end of the previous sweep and
  31   // beginning of this sweep:
  32   //   Count(end_last_sweep) - Count(start_this_sweep)
  33   //     + splitBirths(between) - splitDeaths(between)
  34   // The above number divided by the time since the start [END???] of the
  35   // previous sweep gives us a time rate of demand for blocks
  36   // of this size. We compute a padded average of this rate as
  37   // our current estimate for the time rate of demand for blocks
  38   // of this size. Similarly, we keep a padded average for the time
  39   // between sweeps. Our current estimate for demand for blocks of
  40   // this size is then simply computed as the product of these two
  41   // estimates.
  42   AdaptivePaddedAverage _demand_rate_estimate;
  43 
  44   ssize_t     _desired;          // Estimate computed as described above
  45   ssize_t     _coalDesired;     // desired +/- small-percent for tuning coalescing
  46 
  47   ssize_t     _surplus;         // count - (desired +/- small-percent),
  48                                 // used to tune splitting in best fit
  49   ssize_t     _bfrSurp;         // surplus at start of current sweep
  50   ssize_t     _prevSweep;       // count from end of previous sweep
  51   ssize_t     _beforeSweep;     // count from before current sweep
  52   ssize_t     _coalBirths;      // additional chunks from coalescing
  53   ssize_t     _coalDeaths;      // loss from coalescing
  54   ssize_t     _splitBirths;     // additional chunks from splitting
  55   ssize_t     _splitDeaths;     // loss from splitting
  56   size_t     _returnedBytes;    // number of bytes returned to list.
  57  public:
  58   void initialize() {
  59     AdaptivePaddedAverage* dummy =
  60       new (&_demand_rate_estimate) AdaptivePaddedAverage(CMS_FLSWeight,
  61                                                          CMS_FLSPadding);
  62     _desired = 0;
  63     _coalDesired = 0;
  64     _surplus = 0;
  65     _bfrSurp = 0;
  66     _prevSweep = 0;
  67     _beforeSweep = 0;
  68     _coalBirths = 0;
  69     _coalDeaths = 0;
  70     _splitBirths = 0;
  71     _splitDeaths = 0;
  72     _returnedBytes = 0;
  73   }
  74 
  75   AllocationStats() {
  76     initialize();
  77   }
  78   // The rate estimate is in blocks per second.
  79   void compute_desired(size_t count,
  80                        float inter_sweep_current,
  81                        float inter_sweep_estimate) {
  82     // If the latest inter-sweep time is below our granularity
  83     // of measurement, we may call in here with
  84     // inter_sweep_current == 0. However, even for suitably small
  85     // but non-zero inter-sweep durations, we may not trust the accuracy
  86     // of accumulated data, since it has not been "integrated"
  87     // (read "low-pass-filtered") long enough, and would be
  88     // vulnerable to noisy glitches. In such cases, we
  89     // ignore the current sample and use currently available
  90     // historical estimates.
  91     if (inter_sweep_current > _threshold) {
  92       ssize_t demand = prevSweep() - count + splitBirths() - splitDeaths();
  93       float rate = ((float)demand)/inter_sweep_current;
  94       _demand_rate_estimate.sample(rate);
  95       _desired = (ssize_t)(_demand_rate_estimate.padded_average()
  96                            *inter_sweep_estimate);
  97     }
  98   }
  99 
 100   ssize_t desired() const { return _desired; }
 101   ssize_t coalDesired() const { return _coalDesired; }
 102   void set_coalDesired(ssize_t v) { _coalDesired = v; }
 103 
 104   ssize_t surplus() const { return _surplus; }
 105   void set_surplus(ssize_t v) { _surplus = v; }
 106   void increment_surplus() { _surplus++; }
 107   void decrement_surplus() { _surplus--; }
 108 
 109   ssize_t bfrSurp() const { return _bfrSurp; }
 110   void set_bfrSurp(ssize_t v) { _bfrSurp = v; }
 111   ssize_t prevSweep() const { return _prevSweep; }
 112   void set_prevSweep(ssize_t v) { _prevSweep = v; }
 113   ssize_t beforeSweep() const { return _beforeSweep; }
 114   void set_beforeSweep(ssize_t v) { _beforeSweep = v; }
 115 
 116   ssize_t coalBirths() const { return _coalBirths; }
 117   void set_coalBirths(ssize_t v) { _coalBirths = v; }
 118   void increment_coalBirths() { _coalBirths++; }
 119 
 120   ssize_t coalDeaths() const { return _coalDeaths; }
 121   void set_coalDeaths(ssize_t v) { _coalDeaths = v; }
 122   void increment_coalDeaths() { _coalDeaths++; }
 123 
 124   ssize_t splitBirths() const { return _splitBirths; }
 125   void set_splitBirths(ssize_t v) { _splitBirths = v; }
 126   void increment_splitBirths() { _splitBirths++; }
 127 
 128   ssize_t splitDeaths() const { return _splitDeaths; }
 129   void set_splitDeaths(ssize_t v) { _splitDeaths = v; }
 130   void increment_splitDeaths() { _splitDeaths++; }
 131 
 132   NOT_PRODUCT(
 133     size_t returnedBytes() const { return _returnedBytes; }
 134     void set_returnedBytes(size_t v) { _returnedBytes = v; }
 135   )
 136 };