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annotate packages/kernel/current/cdl/scheduler.cdl @ 76:435cced73e2f ecos-v1_3_1-release

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eCos v1.3.1 merged from eCos master repository on 2000-03-27-23:22:51-BST
author jlarmour
date Tue, 28 Mar 2000 14:10:45 +0000
parents
children 6736c52df507
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435cced73e2f eCos v1.3.1 merged from eCos master repository on 2000-03-27-23:22:51-BST
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1 # ====================================================================
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2 #
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3 # scheduler.cdl
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4 #
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5 # configuration data related to the kernel schedulers
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6 #
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7 # ====================================================================
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8 #####COPYRIGHTBEGIN####
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9 #
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10 # -------------------------------------------
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11 # The contents of this file are subject to the Red Hat eCos Public License
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12 # Version 1.1 (the "License"); you may not use this file except in
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13 # compliance with the License. You may obtain a copy of the License at
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14 # http://www.redhat.com/
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15 #
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16 # Software distributed under the License is distributed on an "AS IS"
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17 # basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
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18 # License for the specific language governing rights and limitations under
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19 # the License.
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20 #
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21 # The Original Code is eCos - Embedded Configurable Operating System,
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22 # released September 30, 1998.
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23 #
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24 # The Initial Developer of the Original Code is Red Hat.
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25 # Portions created by Red Hat are
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26 # Copyright (C) 1998, 1999, 2000 Red Hat, Inc.
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27 # All Rights Reserved.
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28 # -------------------------------------------
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29 #
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30 #####COPYRIGHTEND####
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31 # ====================================================================
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32 ######DESCRIPTIONBEGIN####
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33 #
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34 # Author(s): jskov
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35 # Original data: nickg
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36 # Contributors:
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37 # Date: 1999-07-05
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38 #
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39 #####DESCRIPTIONEND####
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40 #
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41 # ====================================================================
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42
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43 cdl_interface CYGINT_KERNEL_SCHEDULER {
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44 display "Number of schedulers in this configuration"
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45 requires 1 == CYGINT_KERNEL_SCHEDULER
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46 }
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47
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48 # FIXME: The two below options must be mutually exclusive
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49 cdl_option CYGSEM_KERNEL_SCHED_MLQUEUE {
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50 display "Multi-level queue scheduler"
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51 default_value 1
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52 implements CYGINT_KERNEL_SCHEDULER
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53 description "
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54 The multi-level queue scheduler supports multiple priority
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55 levels and multiple threads at each priority level.
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56 Preemption between priority levels is automatic. Timeslicing
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57 within a given priority level is controlled by a separate
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58 configuration option."
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59 }
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60
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61 cdl_option CYGSEM_KERNEL_SCHED_BITMAP {
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62 display "Bitmap scheduler"
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63 default_value 0
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64 implements CYGINT_KERNEL_SCHEDULER
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65 description "
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66 The bitmap scheduler supports multiple priority levels but
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67 only one thread can exist at each priority level. This means
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68 that scheduling decisions are very simple and hence the
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69 scheduler is efficient. Preemption between priority levels is
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70 automatic. Timeslicing within a given priority level is
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71 irrelevant since there can be only one thread at each
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72 priority level."
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73 }
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74
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75 #cdl_option CYGSEM_KERNEL_SCHED_LOTTERY {
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76 # display "Lottery scheduler"
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77 # type radio
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78 # description "
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79 # This scheduler is not yet available."
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80 #}
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81
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82 cdl_option CYGPRI_KERNEL_SCHED_IMPL_HXX {
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83 display "Scheduler header file"
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84 flavor data
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85 description "
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86 This option sets a preprocessor symbol which names the header
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87 file for the selected scheduler. It is used internally by the
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88 common scheduler code to include the correct header file."
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89 calculated { \
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90 CYGSEM_KERNEL_SCHED_BITMAP ? "<cyg/kernel/bitmap.hxx>" :\
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91 CYGSEM_KERNEL_SCHED_MLQUEUE ? "<cyg/kernel/mlqueue.hxx>" :\
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92 CYGSEM_KERNEL_SCHED_LOTTERY ? "<cyg/kernel/lottery.hxx>" :\
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93 "!!!-- Configuration broken - no scheduler selected --!!!"}
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94 }
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95
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96
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97
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98 # NOTE: This option only makes sense if the current scheduler
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99 # supports multiple priority levels.
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100 cdl_component CYGNUM_KERNEL_SCHED_PRIORITIES {
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101 display "Number of priority levels"
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102 flavor data
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103 legal_values 1 to 32
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104 default_value 32
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105 #active_if CYGINT_KERNEL_SCHED_PRIORITY_SCHEDULER
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106 description "
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107 This option controls the number of priority levels that are
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108 available. For some types of scheduler including the bitmap
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109 scheduler this may impose an upper bound on the number of
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110 threads in the system. For other schedulers such as the
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111 mlqueue scheduler the number of threads is independent from
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112 the number of priority levels. Note that the lowest priority
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113 level is normally used only by the idle thread, although
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114 application threads can run at this priority if necessary."
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115
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116 cdl_option CYGNUM_KERNEL_SCHED_BITMAP_SIZE {
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117 display "Bitmap size"
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118 flavor data
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119 calculated {"CYGNUM_KERNEL_SCHED_PRIORITIES"}
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120 description "
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121 This option automatically defines the size of bitmap
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122 used to track occupied priority levels."
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123 }
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124 }
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125
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126
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127 # NOTE: this option only makes sense for some of the schedulers.
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128 # Timeslicing is irrelevant for bitmap schedulers.
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129 cdl_component CYGSEM_KERNEL_SCHED_TIMESLICE {
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130 display "Scheduler timeslicing"
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131 requires !CYGSEM_KERNEL_SCHED_BITMAP
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132 requires CYGVAR_KERNEL_COUNTERS_CLOCK
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133 default_value 1
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134 description "
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135 Some schedulers including the mlqueue scheduler support
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136 timeslicing. This means that the kernel will check regularly
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137 whether or not there is another runnable thread with the
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138 same priority, and if there is such a thread there will be
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139 an automatic context switch. Not all applications require
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140 timeslicing, for example because every thread performs a
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141 blocking operation regularly. For these applications it is
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142 possible to disable timeslicing, which reduces the overheads
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143 associated with timer interrupts."
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144
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145 cdl_option CYGNUM_KERNEL_SCHED_TIMESLICE_TICKS {
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146 display "Number of clock ticks between timeslices"
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147 flavor data
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148 legal_values 1 to 65535
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149 default_value 5
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150 description "
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151 Assuming timeslicing is enabled, how frequently should it
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152 take place? The value of this option corresponds to the
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153 number of clock ticks that should occur before a timeslice
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154 takes place, so increasing the value reduces the frequency
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155 of timeslices."
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156 }
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157 }