342
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1 /*
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2 * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // Keeps track of the GC work and decides when it is OK to do GC work
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26 // and for how long so that the MMU invariants are maintained.
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27
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28 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
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29
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30 // this is the "interface"
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31 class G1MMUTracker {
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32 protected:
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33 double _time_slice;
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34 double _max_gc_time; // this is per time slice
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35
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36 double _conc_overhead_time_sec;
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37
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38 public:
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39 G1MMUTracker(double time_slice, double max_gc_time);
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40
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41 void update_conc_overhead(double conc_overhead);
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42
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43 virtual void add_pause(double start, double end, bool gc_thread) = 0;
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44 virtual double longest_pause(double current_time) = 0;
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45 virtual double when_sec(double current_time, double pause_time) = 0;
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46
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47 double max_gc_time() {
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48 return _max_gc_time - _conc_overhead_time_sec;
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49 }
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50
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51 inline bool now_max_gc(double current_time) {
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52 return when_sec(current_time, max_gc_time()) < 0.00001;
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53 }
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54
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55 inline double when_max_gc_sec(double current_time) {
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56 return when_sec(current_time, max_gc_time());
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57 }
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58
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59 inline jlong when_max_gc_ms(double current_time) {
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60 double when = when_max_gc_sec(current_time);
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61 return (jlong) (when * 1000.0);
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62 }
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63
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64 inline jlong when_ms(double current_time, double pause_time) {
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65 double when = when_sec(current_time, pause_time);
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66 return (jlong) (when * 1000.0);
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67 }
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68 };
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69
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70 class G1MMUTrackerQueueElem {
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71 private:
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72 double _start_time;
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73 double _end_time;
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74
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75 public:
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76 inline double start_time() { return _start_time; }
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77 inline double end_time() { return _end_time; }
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78 inline double duration() { return _end_time - _start_time; }
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79
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80 G1MMUTrackerQueueElem() {
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81 _start_time = 0.0;
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82 _end_time = 0.0;
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83 }
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84
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85 G1MMUTrackerQueueElem(double start_time, double end_time) {
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86 _start_time = start_time;
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87 _end_time = end_time;
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88 }
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89 };
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90
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91 // this is an implementation of the MMUTracker using a (fixed-size) queue
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92 // that keeps track of all the recent pause times
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93 class G1MMUTrackerQueue: public G1MMUTracker {
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94 private:
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95 enum PrivateConstants {
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96 QueueLength = 64
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97 };
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98
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99 // The array keeps track of all the pauses that fall within a time
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100 // slice (the last time slice during which pauses took place).
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101 // The data structure implemented is a circular queue.
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102 // Head "points" to the most recent addition, tail to the oldest one.
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103 // The array is of fixed size and I don't think we'll need more than
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104 // two or three entries with the current behaviour of G1 pauses.
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105 // If the array is full, an easy fix is to look for the pauses with
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106 // the shortest gap between them and concolidate them.
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107
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108 G1MMUTrackerQueueElem _array[QueueLength];
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109 int _head_index;
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110 int _tail_index;
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111 int _no_entries;
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112
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113 inline int trim_index(int index) {
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114 return (index + QueueLength) % QueueLength;
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115 }
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116
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117 void remove_expired_entries(double current_time);
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118 double calculate_gc_time(double current_time);
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119
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120 double longest_pause_internal(double current_time);
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121 double when_internal(double current_time, double pause_time);
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122
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123 public:
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124 G1MMUTrackerQueue(double time_slice, double max_gc_time);
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125
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126 virtual void add_pause(double start, double end, bool gc_thread);
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127
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128 virtual double longest_pause(double current_time);
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129 virtual double when_sec(double current_time, double pause_time);
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130 };
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