1 /*

     2  * Copyright 2001-2007 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 // Keeps track of the GC work and decides when it is OK to do GC work

    26 // and for how long so that the MMU invariants are maintained.

    27 

    28 /***** ALL TIMES ARE IN SECS!!!!!!! *****/

    29 

    30 // this is the "interface"

    31 class G1MMUTracker {

    32 protected:

    33   double          _time_slice;

    34   double          _max_gc_time; // this is per time slice

    35 

    36   double          _conc_overhead_time_sec;

    37 

    38 public:

    39   G1MMUTracker(double time_slice, double max_gc_time);

    40 

    41   void update_conc_overhead(double conc_overhead);

    42 

    43   virtual void add_pause(double start, double end, bool gc_thread) = 0;

    44   virtual double longest_pause(double current_time) = 0;

    45   virtual double when_sec(double current_time, double pause_time) = 0;

    46 

    47   double max_gc_time() {

    48     return _max_gc_time - _conc_overhead_time_sec;

    49   }

    50 

    51   inline bool now_max_gc(double current_time) {

    52     return when_sec(current_time, max_gc_time()) < 0.00001;

    53   }

    54 

    55   inline double when_max_gc_sec(double current_time) {

    56     return when_sec(current_time, max_gc_time());

    57   }

    58 

    59   inline jlong when_max_gc_ms(double current_time) {

    60     double when = when_max_gc_sec(current_time);

    61     return (jlong) (when * 1000.0);

    62   }

    63 

    64   inline jlong when_ms(double current_time, double pause_time) {

    65     double when = when_sec(current_time, pause_time);

    66     return (jlong) (when * 1000.0);

    67   }

    68 };

    69 

    70 class G1MMUTrackerQueueElem {

    71 private:

    72   double _start_time;

    73   double _end_time;

    74 

    75 public:

    76   inline double start_time() { return _start_time; }

    77   inline double end_time()   { return _end_time; }

    78   inline double duration()   { return _end_time - _start_time; }

    79 

    80   G1MMUTrackerQueueElem() {

    81     _start_time = 0.0;

    82     _end_time   = 0.0;

    83   }

    84 

    85   G1MMUTrackerQueueElem(double start_time, double end_time) {

    86     _start_time = start_time;

    87     _end_time   = end_time;

    88   }

    89 };

    90 

    91 // this is an implementation of the MMUTracker using a (fixed-size) queue

    92 // that keeps track of all the recent pause times

    93 class G1MMUTrackerQueue: public G1MMUTracker {

    94 private:

    95   enum PrivateConstants {

    96     QueueLength = 64

    97   };

    98 

    99   // The array keeps track of all the pauses that fall within a time

   100   // slice (the last time slice during which pauses took place).

   101   // The data structure implemented is a circular queue.

   102   // Head "points" to the most recent addition, tail to the oldest one.

   103   // The array is of fixed size and I don't think we'll need more than

   104   // two or three entries with the current behaviour of G1 pauses.

   105   // If the array is full, an easy fix is to look for the pauses with

   106   // the shortest gap between them and concolidate them.

   107 

   108   G1MMUTrackerQueueElem _array[QueueLength];

   109   int                   _head_index;

   110   int                   _tail_index;

   111   int                   _no_entries;

   112 

   113   inline int trim_index(int index) {

   114     return (index + QueueLength) % QueueLength;

   115   }

   116 

   117   void remove_expired_entries(double current_time);

   118   double calculate_gc_time(double current_time);

   119 

   120   double longest_pause_internal(double current_time);

   121   double when_internal(double current_time, double pause_time);

   122 

   123 public:

   124   G1MMUTrackerQueue(double time_slice, double max_gc_time);

   125 

   126   virtual void add_pause(double start, double end, bool gc_thread);

   127 

   128   virtual double longest_pause(double current_time);

   129   virtual double when_sec(double current_time, double pause_time);

   130 };