[ae68ff0] | 1 | @c |
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[4ffbc49] | 2 | @c COPYRIGHT (c) 1988-2007. |
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[ae68ff0] | 3 | @c On-Line Applications Research Corporation (OAR). |
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| 4 | @c All rights reserved. |
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| 5 | @c |
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[139b2e4a] | 6 | @c $Id$ |
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| 7 | @c |
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[ae68ff0] | 8 | |
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| 9 | @c |
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| 10 | @c Open Issues |
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| 11 | @c - nicen up the tables |
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| 12 | @c - use math mode to print formulas |
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| 13 | @c |
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| 14 | |
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| 15 | @chapter Rate Monotonic Manager |
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[20515fc] | 16 | |
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[169502e] | 17 | @cindex rate mononitonic tasks |
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| 18 | @cindex periodic tasks |
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| 19 | |
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[ae68ff0] | 20 | @section Introduction |
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| 21 | |
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[35a81f8] | 22 | The rate monotonic manager provides facilities to implement tasks which execute |
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| 23 | in a periodic fashion. Critically, it also gathers information about the |
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| 24 | execution of those periods and can provide important statistics to the |
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| 25 | user which can be used to analyze and tune the application. The directives |
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| 26 | provided by the rate monotonic manager are: |
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[ae68ff0] | 27 | |
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| 28 | @itemize @bullet |
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[f331481c] | 29 | @item @code{@value{DIRPREFIX}rate_monotonic_create} - Create a rate monotonic period |
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| 30 | @item @code{@value{DIRPREFIX}rate_monotonic_ident} - Get ID of a period |
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| 31 | @item @code{@value{DIRPREFIX}rate_monotonic_cancel} - Cancel a period |
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| 32 | @item @code{@value{DIRPREFIX}rate_monotonic_delete} - Delete a rate monotonic period |
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| 33 | @item @code{@value{DIRPREFIX}rate_monotonic_period} - Conclude current/Start next period |
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[35a81f8] | 34 | @item @code{@value{DIRPREFIX}rate_monotonic_get_status} - Obtain status from a period |
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| 35 | @item @code{@value{DIRPREFIX}rate_monotonic_get_statistics} - Obtain statistics from a period |
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| 36 | @item @code{@value{DIRPREFIX}rate_monotonic_reset_statistics} - Reset statistics for a period |
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| 37 | @item @code{@value{DIRPREFIX}rate_monotonic_reset_all_statistics} - Reset statistics for all periods |
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| 38 | @item @code{@value{DIRPREFIX}rate_monotonic_report_statistics} - Print period statistics report |
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[ae68ff0] | 39 | @end itemize |
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| 40 | |
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| 41 | @section Background |
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| 42 | |
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| 43 | The rate monotonic manager provides facilities to |
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| 44 | manage the execution of periodic tasks. This manager was |
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| 45 | designed to support application designers who utilize the Rate |
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[5ab8aef] | 46 | Monotonic Scheduling Algorithm (RMS) to ensure that their |
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[ae68ff0] | 47 | periodic tasks will meet their deadlines, even under transient |
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| 48 | overload conditions. Although designed for hard real-time |
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| 49 | systems, the services provided by the rate monotonic manager may |
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| 50 | be used by any application which requires periodic tasks. |
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| 51 | |
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[1ca951ce] | 52 | @subsection Rate Monotonic Manager Required Support |
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| 53 | |
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| 54 | A clock tick is required to support the functionality provided by this manager. |
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| 55 | |
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[35a81f8] | 56 | @subsection Period Statistics |
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| 57 | |
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| 58 | This manager maintains a set of statistics on each period. These |
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| 59 | statistics are reset implictly at period creation time and may be |
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| 60 | reset or obtained at any time by the application. The following |
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| 61 | is a list of the information kept: |
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| 62 | |
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| 63 | @itemize @bullet |
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| 64 | @item @code{owner} |
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| 65 | is the id of the thread that owns this period. |
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| 66 | |
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| 67 | @item @code{count} |
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| 68 | is the total number of periods executed. |
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| 69 | |
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| 70 | @item @code{missed_count} |
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| 71 | is the number of periods that were missed. |
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| 72 | |
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| 73 | @item @code{min_cpu_time} |
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| 74 | is the minimum amount of CPU execution time consumed |
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| 75 | on any execution of the periodic loop. |
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| 76 | |
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| 77 | @item @code{max_cpu_time} |
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| 78 | is the maximum amount of CPU execution time consumed |
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| 79 | on any execution of the periodic loop. |
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| 80 | |
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| 81 | @item @code{total_cpu_time} |
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| 82 | is the total amount of CPU execution time consumed |
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| 83 | by executions of the periodic loop. |
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| 84 | |
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| 85 | @item @code{min_wall_time} |
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| 86 | is the minimum amount of wall time that passed |
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| 87 | on any execution of the periodic loop. |
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| 88 | |
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| 89 | @item @code{max_wall_time} |
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| 90 | is the maximum amount of wall time that passed |
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| 91 | on any execution of the periodic loop. |
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| 92 | |
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| 93 | @item @code{total_wall_time} |
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| 94 | is the total amount of wall time that passed |
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| 95 | during executions of the periodic loop. |
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| 96 | |
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| 97 | @end itemize |
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| 98 | |
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| 99 | The period statistics information is inexpensive to maintain |
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| 100 | and can provide very useful insights into the execution |
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| 101 | characteristics of a periodic task loop. But it is just information. |
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| 102 | The period statistics reported must be analyzed by the user in terms |
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| 103 | of what the applications is. For example, in an application where |
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| 104 | priorities are assigned by the Rate Monotonic Algorithm, it would |
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| 105 | be very undesirable for high priority (i.e. frequency) tasks to |
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| 106 | miss their period. Similarly, in nearly any application, if a |
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| 107 | task were supposed to execute its periodic loop every 10 milliseconds |
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| 108 | and it averaged 11 milliseconds, then application requirements |
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| 109 | are not being met. |
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| 110 | |
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| 111 | The information reported can be used to determine the "hot spots" |
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| 112 | in the application. Given a period's id, the user can determine |
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| 113 | the length of that period. From that information and the CPU usage, |
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| 114 | the user can calculate the percentage of CPU time consumed by that |
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| 115 | periodic task. For example, a task executing for 20 milliseconds |
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| 116 | every 200 milliseconds is consuming 10 percent of the processor's |
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| 117 | execution time. This is usually enough to make it a good candidate |
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| 118 | for optimization. |
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| 119 | |
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| 120 | However, execution time alone is not enough to gauge the value of |
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| 121 | optimizing a particular task. It is more important to optimize |
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| 122 | a task executing 2 millisecond every 10 milliseconds (20 percent |
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| 123 | of the CPU) than one executing 10 milliseconds every 100 (10 percent |
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| 124 | of the CPU). As a general rule of thumb, the higher frequency at |
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| 125 | which a task executes, the more important it is to optimize that |
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| 126 | task. |
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| 127 | |
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[ae68ff0] | 128 | @subsection Rate Monotonic Manager Definitions |
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| 129 | |
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[169502e] | 130 | @cindex periodic task, definition |
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| 131 | |
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[ae68ff0] | 132 | A periodic task is one which must be executed at a |
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| 133 | regular interval. The interval between successive iterations of |
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| 134 | the task is referred to as its period. Periodic tasks can be |
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| 135 | characterized by the length of their period and execution time. |
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| 136 | The period and execution time of a task can be used to determine |
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| 137 | the processor utilization for that task. Processor utilization |
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| 138 | is the percentage of processor time used and can be calculated |
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| 139 | on a per-task or system-wide basis. Typically, the task's |
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| 140 | worst-case execution time will be less than its period. For |
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| 141 | example, a periodic task's requirements may state that it should |
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| 142 | execute for 10 milliseconds every 100 milliseconds. Although |
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| 143 | the execution time may be the average, worst, or best case, the |
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| 144 | worst-case execution time is more appropriate for use when |
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| 145 | analyzing system behavior under transient overload conditions. |
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| 146 | |
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[169502e] | 147 | @cindex aperiodic task, definition |
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| 148 | |
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[ae68ff0] | 149 | In contrast, an aperiodic task executes at irregular |
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| 150 | intervals and has only a soft deadline. In other words, the |
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| 151 | deadlines for aperiodic tasks are not rigid, but adequate |
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| 152 | response times are desirable. For example, an aperiodic task |
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| 153 | may process user input from a terminal. |
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| 154 | |
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[169502e] | 155 | @cindex sporadic task, definition |
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| 156 | |
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[ae68ff0] | 157 | Finally, a sporadic task is an aperiodic task with a |
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| 158 | hard deadline and minimum interarrival time. The minimum |
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| 159 | interarrival time is the minimum period of time which exists |
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| 160 | between successive iterations of the task. For example, a |
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| 161 | sporadic task could be used to process the pressing of a fire |
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| 162 | button on a joystick. The mechanical action of the fire button |
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[5ab8aef] | 163 | ensures a minimum time period between successive activations, |
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[ae68ff0] | 164 | but the missile must be launched by a hard deadline. |
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| 165 | |
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| 166 | @subsection Rate Monotonic Scheduling Algorithm |
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| 167 | |
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[169502e] | 168 | @cindex Rate Monotonic Scheduling Algorithm, definition |
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| 169 | @cindex RMS Algorithm, definition |
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| 170 | |
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[ae68ff0] | 171 | The Rate Monotonic Scheduling Algorithm (RMS) is |
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| 172 | important to real-time systems designers because it allows one |
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| 173 | to guarantee that a set of tasks is schedulable. A set of tasks |
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| 174 | is said to be schedulable if all of the tasks can meet their |
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| 175 | deadlines. RMS provides a set of rules which can be used to |
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| 176 | perform a guaranteed schedulability analysis for a task set. |
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| 177 | This analysis determines whether a task set is schedulable under |
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| 178 | worst-case conditions and emphasizes the predictability of the |
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| 179 | system's behavior. It has been proven that: |
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| 180 | |
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| 181 | @itemize @code{ } |
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| 182 | @b{RMS is an optimal static priority algorithm for |
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| 183 | scheduling independent, preemptible, periodic tasks |
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| 184 | on a single processor.} |
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| 185 | @end itemize |
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| 186 | |
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| 187 | RMS is optimal in the sense that if a set of tasks |
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| 188 | can be scheduled by any static priority algorithm, then RMS will |
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| 189 | be able to schedule that task set. RMS bases it schedulability |
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| 190 | analysis on the processor utilization level below which all |
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| 191 | deadlines can be met. |
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| 192 | |
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| 193 | RMS calls for the static assignment of task |
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| 194 | priorities based upon their period. The shorter a task's |
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| 195 | period, the higher its priority. For example, a task with a 1 |
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| 196 | millisecond period has higher priority than a task with a 100 |
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[87dea1e4] | 197 | millisecond period. If two tasks have the same period, then RMS |
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[ae68ff0] | 198 | does not distinguish between the tasks. However, RTEMS |
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| 199 | specifies that when given tasks of equal priority, the task |
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| 200 | which has been ready longest will execute first. RMS's priority |
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| 201 | assignment scheme does not provide one with exact numeric values |
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| 202 | for task priorities. For example, consider the following task |
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| 203 | set and priority assignments: |
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| 204 | |
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| 205 | @ifset use-ascii |
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| 206 | @example |
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| 207 | @group |
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| 208 | +--------------------+---------------------+---------------------+ |
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| 209 | | Task | Period | Priority | |
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| 210 | | | (in milliseconds) | | |
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| 211 | +--------------------+---------------------+---------------------+ |
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| 212 | | 1 | 100 | Low | |
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| 213 | +--------------------+---------------------+---------------------+ |
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| 214 | | 2 | 50 | Medium | |
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| 215 | +--------------------+---------------------+---------------------+ |
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| 216 | | 3 | 50 | Medium | |
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| 217 | +--------------------+---------------------+---------------------+ |
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| 218 | | 4 | 25 | High | |
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| 219 | +--------------------+---------------------+---------------------+ |
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| 220 | @end group |
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| 221 | @end example |
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| 222 | @end ifset |
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| 223 | |
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| 224 | @ifset use-tex |
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| 225 | @sp 1 |
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| 226 | @tex |
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| 227 | \centerline{\vbox{\offinterlineskip\halign{ |
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| 228 | \vrule\strut#& |
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| 229 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
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| 230 | \vrule#& |
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| 231 | \hbox to 1.25in{\enskip\hfil#\hfil}& |
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| 232 | \vrule#& |
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| 233 | \hbox to 1.25in{\enskip\hfil#\hfil}& |
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| 234 | \vrule#\cr\noalign{\hrule} |
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| 235 | &\bf Task&& \bf Period && \bf Priority &\cr |
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| 236 | & && \bf (in milliseconds) && &\cr\noalign{\hrule} |
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| 237 | & 1 && 100 && Low &\cr\noalign{\hrule} |
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| 238 | & 2 && 50 && Medium &\cr\noalign{\hrule} |
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| 239 | & 3 && 50 && Medium &\cr\noalign{\hrule} |
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[1ca951ce] | 240 | & 4 && 25 && High &\cr\noalign{\hrule} |
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[ae68ff0] | 241 | }}\hfil} |
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| 242 | @end tex |
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| 243 | @end ifset |
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| 244 | |
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| 245 | @ifset use-html |
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| 246 | @html |
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| 247 | <CENTER> |
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| 248 | <TABLE COLS=3 WIDTH="80%" BORDER=2> |
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| 249 | <TR><TD ALIGN=center><STRONG>Task</STRONG></TD> |
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| 250 | <TD ALIGN=center><STRONG>Period (in milliseconds)</STRONG></TD> |
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| 251 | <TD ALIGN=center><STRONG>Priority</STRONG></TD></TR> |
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| 252 | <TR><TD ALIGN=center>1</TD> |
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| 253 | <TD ALIGN=center>100 </TD> |
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| 254 | <TD ALIGN=center>Low</TD></TR> |
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| 255 | <TR><TD ALIGN=center>2</TD> |
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| 256 | <TD ALIGN=center>50 </TD> |
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| 257 | <TD ALIGN=center>Medium</TD></TR> |
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| 258 | <TR><TD ALIGN=center>3</TD> |
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| 259 | <TD ALIGN=center>50 </TD> |
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| 260 | <TD ALIGN=center>Medium</TD></TR> |
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| 261 | <TR><TD ALIGN=center>4</TD> |
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| 262 | <TD ALIGN=center>25 </TD> |
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| 263 | <TD ALIGN=center>High</TD></TR> |
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| 264 | </TABLE> |
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| 265 | </CENTER> |
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| 266 | @end html |
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| 267 | @end ifset |
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| 268 | |
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| 269 | RMS only calls for task 1 to have the lowest |
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| 270 | priority, task 4 to have the highest priority, and tasks 2 and 3 |
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| 271 | to have an equal priority between that of tasks 1 and 4. The |
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| 272 | actual RTEMS priorities assigned to the tasks must only adhere |
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| 273 | to those guidelines. |
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| 274 | |
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| 275 | Many applications have tasks with both hard and soft |
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| 276 | deadlines. The tasks with hard deadlines are typically referred |
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| 277 | to as the critical task set, with the soft deadline tasks being |
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| 278 | the non-critical task set. The critical task set can be |
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| 279 | scheduled using RMS, with the non-critical tasks not executing |
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| 280 | under transient overload, by simply assigning priorities such |
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| 281 | that the lowest priority critical task (i.e. longest period) has |
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| 282 | a higher priority than the highest priority non-critical task. |
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| 283 | Although RMS may be used to assign priorities to the |
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| 284 | non-critical tasks, it is not necessary. In this instance, |
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| 285 | schedulability is only guaranteed for the critical task set. |
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| 286 | |
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| 287 | @subsection Schedulability Analysis |
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| 288 | |
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[169502e] | 289 | @cindex RMS schedulability analysis |
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| 290 | |
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[5ab8aef] | 291 | RMS allows application designers to ensure that tasks |
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[ae68ff0] | 292 | can meet all deadlines, even under transient overload, without |
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| 293 | knowing exactly when any given task will execute by applying |
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| 294 | proven schedulability analysis rules. |
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| 295 | |
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[44e7129] | 296 | @subsubsection Assumptions |
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[ae68ff0] | 297 | |
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| 298 | The schedulability analysis rules for RMS were |
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| 299 | developed based on the following assumptions: |
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| 300 | |
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| 301 | |
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| 302 | @itemize @bullet |
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| 303 | @item The requests for all tasks for which hard deadlines |
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| 304 | exist are periodic, with a constant interval between requests. |
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| 305 | |
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| 306 | @item Each task must complete before the next request for it |
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| 307 | occurs. |
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| 308 | |
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| 309 | @item The tasks are independent in that a task does not depend |
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| 310 | on the initiation or completion of requests for other tasks. |
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| 311 | |
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| 312 | @item The execution time for each task without preemption or |
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| 313 | interruption is constant and does not vary. |
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| 314 | |
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| 315 | @item Any non-periodic tasks in the system are special. These |
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| 316 | tasks displace periodic tasks while executing and do not have |
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| 317 | hard, critical deadlines. |
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| 318 | @end itemize |
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| 319 | |
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| 320 | Once the basic schedulability analysis is understood, |
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| 321 | some of the above assumptions can be relaxed and the |
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| 322 | side-effects accounted for. |
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| 323 | |
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[44e7129] | 324 | @subsubsection Processor Utilization Rule |
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[ae68ff0] | 325 | |
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[169502e] | 326 | @cindex RMS Processor Utilization Rule |
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| 327 | |
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[ae68ff0] | 328 | The Processor Utilization Rule requires that |
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| 329 | processor utilization be calculated based upon the period and |
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| 330 | execution time of each task. The fraction of processor time |
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| 331 | spent executing task index is Time(index) / Period(index). The |
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| 332 | processor utilization can be calculated as follows: |
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| 333 | |
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| 334 | @example |
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| 335 | @group |
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| 336 | Utilization = 0 |
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| 337 | |
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| 338 | for index = 1 to maximum_tasks |
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| 339 | Utilization = Utilization + (Time(index)/Period(index)) |
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| 340 | @end group |
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| 341 | @end example |
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| 342 | |
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[5ab8aef] | 343 | To ensure schedulability even under transient |
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[ae68ff0] | 344 | overload, the processor utilization must adhere to the following |
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| 345 | rule: |
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| 346 | |
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| 347 | @example |
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[af61bca7] | 348 | Utilization = maximum_tasks * (2**(1/maximum_tasks) - 1) |
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[ae68ff0] | 349 | @end example |
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| 350 | |
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| 351 | As the number of tasks increases, the above formula |
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| 352 | approaches ln(2) for a worst-case utilization factor of |
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| 353 | approximately 0.693. Many tasks sets can be scheduled with a |
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| 354 | greater utilization factor. In fact, the average processor |
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| 355 | utilization threshold for a randomly generated task set is |
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| 356 | approximately 0.88. |
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| 357 | |
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[44e7129] | 358 | @subsubsection Processor Utilization Rule Example |
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[ae68ff0] | 359 | |
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| 360 | This example illustrates the application of the |
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| 361 | Processor Utilization Rule to an application with three critical |
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| 362 | periodic tasks. The following table details the RMS priority, |
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| 363 | period, execution time, and processor utilization for each task: |
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| 364 | |
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| 365 | @ifset use-ascii |
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| 366 | @example |
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| 367 | @group |
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| 368 | +------------+----------+--------+-----------+-------------+ |
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| 369 | | Task | RMS | Period | Execution | Processor | |
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| 370 | | | Priority | | Time | Utilization | |
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| 371 | +------------+----------+--------+-----------+-------------+ |
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| 372 | | 1 | High | 100 | 15 | 0.15 | |
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| 373 | +------------+----------+--------+-----------+-------------+ |
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| 374 | | 2 | Medium | 200 | 50 | 0.25 | |
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| 375 | +------------+----------+--------+-----------+-------------+ |
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| 376 | | 3 | Low | 300 | 100 | 0.33 | |
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| 377 | +------------+----------+--------+-----------+-------------+ |
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| 378 | @end group |
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| 379 | @end example |
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| 380 | @end ifset |
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| 381 | |
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| 382 | @ifset use-tex |
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| 383 | @sp 1 |
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| 384 | @tex |
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| 385 | \centerline{\vbox{\offinterlineskip\halign{ |
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| 386 | \vrule\strut#& |
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| 387 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
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| 388 | \vrule#& |
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| 389 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
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| 390 | \vrule#& |
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| 391 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
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| 392 | \vrule#& |
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| 393 | \hbox to 1.00in{\enskip\hfil#\hfil}& |
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| 394 | \vrule#& |
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| 395 | \hbox to 1.00in{\enskip\hfil#\hfil}& |
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| 396 | \vrule#\cr\noalign{\hrule} |
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| 397 | &\bf Task&& \bf RMS && \bf Period && \bf Execution &&\bf Processor&\cr |
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| 398 | & && \bf Priority && &&\bf Time &&\bf Utilization &\cr\noalign{\hrule} |
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| 399 | & 1 && High && 100 && 15 && 0.15 &\cr\noalign{\hrule} |
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| 400 | & 2 && Medium && 200 && 50 && 0.25 &\cr\noalign{\hrule} |
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| 401 | & 3 && Low && 300 && 100 && 0.33 &\cr\noalign{\hrule} |
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| 402 | }}\hfil} |
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| 403 | @end tex |
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| 404 | @end ifset |
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| 405 | |
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| 406 | @ifset use-html |
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| 407 | @html |
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| 408 | <CENTER> |
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| 409 | <TABLE COLS=5 WIDTH="80%" BORDER=2> |
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| 410 | <TR><TD ALIGN=center><STRONG>Task</STRONG></TD> |
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| 411 | <TD ALIGN=center><STRONG>RMS Priority</STRONG></TD> |
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| 412 | <TD ALIGN=center><STRONG>Period</STRONG></TD> |
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| 413 | <TD ALIGN=center><STRONG>Execution Time</STRONG></TD> |
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| 414 | <TD ALIGN=center><STRONG>Processor Utilization</STRONG></TD></TR> |
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| 415 | <TR><TD ALIGN=center>1</TD> |
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| 416 | <TD ALIGN=center>High</TD> |
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| 417 | <TD ALIGN=center>100</TD> |
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| 418 | <TD ALIGN=center>15</TD> |
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| 419 | <TD ALIGN=center>0.15</TD></TR> |
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| 420 | <TR><TD ALIGN=center>2</TD> |
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| 421 | <TD ALIGN=center>Medium</TD> |
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| 422 | <TD ALIGN=center>200</TD> |
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| 423 | <TD ALIGN=center>50</TD> |
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| 424 | <TD ALIGN=center>0.25</TD></TR> |
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| 425 | <TR><TD ALIGN=center>3</TD> |
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| 426 | <TD ALIGN=center>Low</TD> |
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| 427 | <TD ALIGN=center>300</TD> |
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| 428 | <TD ALIGN=center>100</TD> |
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| 429 | <TD ALIGN=center>0.33</TD></TR> |
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| 430 | </TABLE> |
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| 431 | </CENTER> |
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| 432 | @end html |
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| 433 | @end ifset |
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| 434 | |
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| 435 | The total processor utilization for this task set is |
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[af61bca7] | 436 | 0.73 which is below the upper bound of 3 * (2**(1/3) - 1), or |
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[ae68ff0] | 437 | 0.779, imposed by the Processor Utilization Rule. Therefore, |
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| 438 | this task set is guaranteed to be schedulable using RMS. |
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| 439 | |
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[44e7129] | 440 | @subsubsection First Deadline Rule |
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[ae68ff0] | 441 | |
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[169502e] | 442 | @cindex RMS First Deadline Rule |
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| 443 | |
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[ae68ff0] | 444 | If a given set of tasks do exceed the processor |
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| 445 | utilization upper limit imposed by the Processor Utilization |
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| 446 | Rule, they can still be guaranteed to meet all their deadlines |
---|
| 447 | by application of the First Deadline Rule. This rule can be |
---|
| 448 | stated as follows: |
---|
| 449 | |
---|
| 450 | For a given set of independent periodic tasks, if |
---|
| 451 | each task meets its first deadline when all tasks are started at |
---|
| 452 | the same time, then the deadlines will always be met for any |
---|
| 453 | combination of start times. |
---|
| 454 | |
---|
| 455 | A key point with this rule is that ALL periodic tasks |
---|
| 456 | are assumed to start at the exact same instant in time. |
---|
| 457 | Although this assumption may seem to be invalid, RTEMS makes it |
---|
[5ab8aef] | 458 | quite easy to ensure. By having a non-preemptible user |
---|
[ae68ff0] | 459 | initialization task, all application tasks, regardless of |
---|
| 460 | priority, can be created and started before the initialization |
---|
[5ab8aef] | 461 | deletes itself. This technique ensures that all tasks begin to |
---|
[ae68ff0] | 462 | compete for execution time at the same instant -- when the user |
---|
| 463 | initialization task deletes itself. |
---|
| 464 | |
---|
[44e7129] | 465 | @subsubsection First Deadline Rule Example |
---|
[ae68ff0] | 466 | |
---|
[5ab8aef] | 467 | The First Deadline Rule can ensure schedulability |
---|
[ae68ff0] | 468 | even when the Processor Utilization Rule fails. The example |
---|
| 469 | below is a modification of the Processor Utilization Rule |
---|
| 470 | example where task execution time has been increased from 15 to |
---|
| 471 | 25 units. The following table details the RMS priority, period, |
---|
| 472 | execution time, and processor utilization for each task: |
---|
| 473 | |
---|
| 474 | @ifset use-ascii |
---|
| 475 | @example |
---|
| 476 | @group |
---|
| 477 | +------------+----------+--------+-----------+-------------+ |
---|
| 478 | | Task | RMS | Period | Execution | Processor | |
---|
| 479 | | | Priority | | Time | Utilization | |
---|
| 480 | +------------+----------+--------+-----------+-------------+ |
---|
| 481 | | 1 | High | 100 | 25 | 0.25 | |
---|
| 482 | +------------+----------+--------+-----------+-------------+ |
---|
| 483 | | 2 | Medium | 200 | 50 | 0.25 | |
---|
| 484 | +------------+----------+--------+-----------+-------------+ |
---|
| 485 | | 3 | Low | 300 | 100 | 0.33 | |
---|
| 486 | +------------+----------+--------+-----------+-------------+ |
---|
| 487 | @end group |
---|
| 488 | @end example |
---|
| 489 | @end ifset |
---|
| 490 | |
---|
| 491 | @ifset use-tex |
---|
| 492 | @sp 1 |
---|
| 493 | @tex |
---|
| 494 | \centerline{\vbox{\offinterlineskip\halign{ |
---|
| 495 | \vrule\strut#& |
---|
| 496 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
---|
| 497 | \vrule#& |
---|
| 498 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
---|
| 499 | \vrule#& |
---|
| 500 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
---|
| 501 | \vrule#& |
---|
| 502 | \hbox to 1.00in{\enskip\hfil#\hfil}& |
---|
| 503 | \vrule#& |
---|
| 504 | \hbox to 1.00in{\enskip\hfil#\hfil}& |
---|
| 505 | \vrule#\cr\noalign{\hrule} |
---|
| 506 | &\bf Task&& \bf RMS && \bf Period && \bf Execution &&\bf Processor&\cr |
---|
| 507 | & && \bf Priority && &&\bf Time &&\bf Utilization &\cr\noalign{\hrule} |
---|
| 508 | & 1 && High && 100 && 25 && 0.25 &\cr\noalign{\hrule} |
---|
| 509 | & 2 && Medium && 200 && 50 && 0.25 &\cr\noalign{\hrule} |
---|
| 510 | & 3 && Low && 300 && 100 && 0.33 &\cr\noalign{\hrule} |
---|
| 511 | }}\hfil} |
---|
| 512 | @end tex |
---|
| 513 | @end ifset |
---|
| 514 | |
---|
| 515 | @ifset use-html |
---|
| 516 | @html |
---|
| 517 | <CENTER> |
---|
| 518 | <TABLE COLS=5 WIDTH="80%" BORDER=2> |
---|
| 519 | <TR><TD ALIGN=center><STRONG>Task</STRONG></TD> |
---|
| 520 | <TD ALIGN=center><STRONG>RMS Priority</STRONG></TD> |
---|
| 521 | <TD ALIGN=center><STRONG>Period</STRONG></TD> |
---|
| 522 | <TD ALIGN=center><STRONG>Execution Time</STRONG></TD> |
---|
| 523 | <TD ALIGN=center><STRONG>Processor Utilization</STRONG></TD></TR> |
---|
| 524 | <TR><TD ALIGN=center>1</TD> |
---|
| 525 | <TD ALIGN=center>High</TD> |
---|
| 526 | <TD ALIGN=center>100</TD> |
---|
| 527 | <TD ALIGN=center>25</TD> |
---|
| 528 | <TD ALIGN=center>0.25</TD></TR> |
---|
| 529 | <TR><TD ALIGN=center>2</TD> |
---|
| 530 | <TD ALIGN=center>Medium</TD> |
---|
| 531 | <TD ALIGN=center>200</TD> |
---|
| 532 | <TD ALIGN=center>50</TD> |
---|
| 533 | <TD ALIGN=center>0.25</TD></TR> |
---|
| 534 | <TR><TD ALIGN=center>3</TD> |
---|
| 535 | <TD ALIGN=center>Low</TD> |
---|
| 536 | <TD ALIGN=center>300</TD> |
---|
| 537 | <TD ALIGN=center>100</TD> |
---|
| 538 | <TD ALIGN=center>0.33</TD></TR> |
---|
| 539 | </TABLE> |
---|
| 540 | </CENTER> |
---|
| 541 | @end html |
---|
| 542 | @end ifset |
---|
| 543 | |
---|
| 544 | The total processor utilization for the modified task |
---|
[af61bca7] | 545 | set is 0.83 which is above the upper bound of 3 * (2**(1/3) - 1), |
---|
[ae68ff0] | 546 | or 0.779, imposed by the Processor Utilization Rule. Therefore, |
---|
| 547 | this task set is not guaranteed to be schedulable using RMS. |
---|
| 548 | However, the First Deadline Rule can guarantee the |
---|
| 549 | schedulability of this task set. This rule calls for one to |
---|
| 550 | examine each occurrence of deadline until either all tasks have |
---|
| 551 | met their deadline or one task failed to meet its first |
---|
| 552 | deadline. The following table details the time of each deadline |
---|
| 553 | occurrence, the maximum number of times each task may have run, |
---|
| 554 | the total execution time, and whether all the deadlines have |
---|
| 555 | been met. |
---|
| 556 | |
---|
| 557 | @ifset use-ascii |
---|
| 558 | @example |
---|
| 559 | @group |
---|
| 560 | +----------+------+------+------+----------------------+---------------+ |
---|
| 561 | | Deadline | Task | Task | Task | Total | All Deadlines | |
---|
| 562 | | Time | 1 | 2 | 3 | Execution Time | Met? | |
---|
| 563 | +----------+------+------+------+----------------------+---------------+ |
---|
| 564 | | 100 | 1 | 1 | 1 | 25 + 50 + 100 = 175 | NO | |
---|
| 565 | +----------+------+------+------+----------------------+---------------+ |
---|
| 566 | | 200 | 2 | 1 | 1 | 50 + 50 + 100 = 200 | YES | |
---|
| 567 | +----------+------+------+------+----------------------+---------------+ |
---|
| 568 | @end group |
---|
| 569 | @end example |
---|
| 570 | @end ifset |
---|
| 571 | |
---|
| 572 | @ifset use-tex |
---|
| 573 | @sp 1 |
---|
| 574 | @tex |
---|
| 575 | \centerline{\vbox{\offinterlineskip\halign{ |
---|
| 576 | \vrule\strut#& |
---|
| 577 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
---|
| 578 | \vrule#& |
---|
| 579 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
---|
| 580 | \vrule#& |
---|
| 581 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
---|
| 582 | \vrule#& |
---|
| 583 | \hbox to 0.75in{\enskip\hfil#\hfil}& |
---|
| 584 | \vrule#& |
---|
| 585 | \hbox to 2.00in{\enskip\hfil#\hfil}& |
---|
| 586 | \vrule#& |
---|
| 587 | \hbox to 1.00in{\enskip\hfil#\hfil}& |
---|
| 588 | \vrule#\cr\noalign{\hrule} |
---|
| 589 | &\bf Deadline&& \bf Task &&\bf Task&&\bf Task&&\bf Total &&\bf All Deadlines &\cr |
---|
| 590 | &\bf Time && \bf 1 &&\bf 2 &&\bf 3 &&\bf Execution Time &&\bf Net?&\cr\noalign{\hrule} |
---|
| 591 | & 100&& 1 && 1 && 1 && 25 + 50 + 100 = 175 && NO &\cr\noalign{\hrule} |
---|
| 592 | & 200&& 2 && 1 && 1 && 50 + 50 + 100 = 200 && YES &\cr\noalign{\hrule} |
---|
| 593 | }}\hfil} |
---|
| 594 | @end tex |
---|
| 595 | @end ifset |
---|
| 596 | |
---|
| 597 | @ifset use-html |
---|
| 598 | @html |
---|
| 599 | <CENTER> |
---|
| 600 | <TABLE COLS=6 WIDTH="80%" BORDER=2> |
---|
| 601 | <TR><TD ALIGN=center><STRONG>Deadline Time</STRONG></TD> |
---|
| 602 | <TD ALIGN=center><STRONG>Task 1</STRONG></TD> |
---|
| 603 | <TD ALIGN=center><STRONG>Task 2</STRONG></TD> |
---|
| 604 | <TD ALIGN=center><STRONG>Task 3</STRONG></TD> |
---|
| 605 | <TD ALIGN=center><STRONG>Total Execution Time</STRONG></TD> |
---|
| 606 | <TD ALIGN=center><STRONG>All Deadlines Met?</STRONG></TD></TR> |
---|
| 607 | <TR><TD ALIGN=center>100</TD> |
---|
| 608 | <TD ALIGN=center>1</TD> |
---|
| 609 | <TD ALIGN=center>1</TD> |
---|
| 610 | <TD ALIGN=center>1</TD> |
---|
| 611 | <TD ALIGN=center>25 + 50 + 100 = 175</TD> |
---|
| 612 | <TD ALIGN=center>NO</TD></TR> |
---|
| 613 | <TR><TD ALIGN=center>200</TD> |
---|
| 614 | <TD ALIGN=center>2</TD> |
---|
| 615 | <TD ALIGN=center>1</TD> |
---|
| 616 | <TD ALIGN=center>1</TD> |
---|
| 617 | <TD ALIGN=center>50 + 50 + 100 = 175</TD> |
---|
| 618 | <TD ALIGN=center>YES</TD></TR> |
---|
| 619 | </TABLE> |
---|
| 620 | </CENTER> |
---|
| 621 | @end html |
---|
| 622 | @end ifset |
---|
| 623 | |
---|
| 624 | The key to this analysis is to recognize when each |
---|
| 625 | task will execute. For example at time 100, task 1 must have |
---|
| 626 | met its first deadline, but tasks 2 and 3 may also have begun |
---|
| 627 | execution. In this example, at time 100 tasks 1 and 2 have |
---|
| 628 | completed execution and thus have met their first deadline. |
---|
| 629 | Tasks 1 and 2 have used (25 + 50) = 75 time units, leaving (100 |
---|
| 630 | - 75) = 25 time units for task 3 to begin. Because task 3 takes |
---|
| 631 | 100 ticks to execute, it will not have completed execution at |
---|
| 632 | time 100. Thus at time 100, all of the tasks except task 3 have |
---|
| 633 | met their first deadline. |
---|
| 634 | |
---|
| 635 | At time 200, task 1 must have met its second deadline |
---|
| 636 | and task 2 its first deadline. As a result, of the first 200 |
---|
| 637 | time units, task 1 uses (2 * 25) = 50 and task 2 uses 50, |
---|
| 638 | leaving (200 - 100) time units for task 3. Task 3 requires 100 |
---|
| 639 | time units to execute, thus it will have completed execution at |
---|
| 640 | time 200. Thus, all of the tasks have met their first deadlines |
---|
| 641 | at time 200, and the task set is schedulable using the First |
---|
| 642 | Deadline Rule. |
---|
| 643 | |
---|
[44e7129] | 644 | @subsubsection Relaxation of Assumptions |
---|
[ae68ff0] | 645 | |
---|
| 646 | The assumptions used to develop the RMS |
---|
| 647 | schedulability rules are uncommon in most real-time systems. |
---|
| 648 | For example, it was assumed that tasks have constant unvarying |
---|
| 649 | execution time. It is possible to relax this assumption, simply |
---|
| 650 | by using the worst-case execution time of each task. |
---|
| 651 | |
---|
| 652 | Another assumption is that the tasks are independent. |
---|
| 653 | This means that the tasks do not wait for one another or |
---|
| 654 | contend for resources. This assumption can be relaxed by |
---|
| 655 | accounting for the amount of time a task spends waiting to |
---|
| 656 | acquire resources. Similarly, each task's execution time must |
---|
| 657 | account for any I/O performed and any RTEMS directive calls. |
---|
| 658 | |
---|
| 659 | In addition, the assumptions did not account for the |
---|
| 660 | time spent executing interrupt service routines. This can be |
---|
| 661 | accounted for by including all the processor utilization by |
---|
| 662 | interrupt service routines in the utilization calculation. |
---|
| 663 | Similarly, one should also account for the impact of delays in |
---|
| 664 | accessing local memory caused by direct memory access and other |
---|
| 665 | processors accessing local dual-ported memory. |
---|
| 666 | |
---|
| 667 | The assumption that nonperiodic tasks are used only |
---|
| 668 | for initialization or failure-recovery can be relaxed by placing |
---|
| 669 | all periodic tasks in the critical task set. This task set can |
---|
| 670 | be scheduled and analyzed using RMS. All nonperiodic tasks are |
---|
| 671 | placed in the non-critical task set. Although the critical task |
---|
| 672 | set can be guaranteed to execute even under transient overload, |
---|
| 673 | the non-critical task set is not guaranteed to execute. |
---|
| 674 | |
---|
| 675 | In conclusion, the application designer must be fully |
---|
| 676 | cognizant of the system and its run-time behavior when |
---|
| 677 | performing schedulability analysis for a system using RMS. |
---|
| 678 | Every hardware and software factor which impacts the execution |
---|
| 679 | time of each task must be accounted for in the schedulability |
---|
| 680 | analysis. |
---|
| 681 | |
---|
[44e7129] | 682 | @subsubsection Further Reading |
---|
[ae68ff0] | 683 | |
---|
| 684 | For more information on Rate Monotonic Scheduling and |
---|
| 685 | its schedulability analysis, the reader is referred to the |
---|
| 686 | following: |
---|
| 687 | |
---|
| 688 | @itemize @code{ } |
---|
| 689 | @item @cite{C. L. Liu and J. W. Layland. "Scheduling Algorithms for |
---|
| 690 | Multiprogramming in a Hard Real Time Environment." @b{Journal of |
---|
| 691 | the Association of Computing Machinery}. January 1973. pp. 46-61.} |
---|
| 692 | |
---|
| 693 | @item @cite{John Lehoczky, Lui Sha, and Ye Ding. "The Rate Monotonic |
---|
| 694 | Scheduling Algorithm: Exact Characterization and Average Case |
---|
| 695 | Behavior." @b{IEEE Real-Time Systems Symposium}. 1989. pp. 166-171.} |
---|
| 696 | |
---|
| 697 | @item @cite{Lui Sha and John Goodenough. "Real-Time Scheduling |
---|
| 698 | Theory and Ada." @b{IEEE Computer}. April 1990. pp. 53-62.} |
---|
| 699 | |
---|
| 700 | @item @cite{Alan Burns. "Scheduling hard real-time systems: a |
---|
| 701 | review." @b{Software Engineering Journal}. May 1991. pp. 116-128.} |
---|
| 702 | @end itemize |
---|
| 703 | |
---|
| 704 | @section Operations |
---|
[20515fc] | 705 | |
---|
[ae68ff0] | 706 | @subsection Creating a Rate Monotonic Period |
---|
| 707 | |
---|
[75e22db] | 708 | The @code{@value{DIRPREFIX}rate_monotonic_create} directive creates a rate |
---|
[ae68ff0] | 709 | monotonic period which is to be used by the calling task to |
---|
| 710 | delineate a period. RTEMS allocates a Period Control Block |
---|
| 711 | (PCB) from the PCB free list. This data structure is used by |
---|
| 712 | RTEMS to manage the newly created rate monotonic period. RTEMS |
---|
| 713 | returns a unique period ID to the application which is used by |
---|
| 714 | other rate monotonic manager directives to access this rate |
---|
| 715 | monotonic period. |
---|
| 716 | |
---|
| 717 | @subsection Manipulating a Period |
---|
| 718 | |
---|
[75e22db] | 719 | The @code{@value{DIRPREFIX}rate_monotonic_period} directive is used to |
---|
[ae68ff0] | 720 | establish and maintain periodic execution utilizing a previously |
---|
| 721 | created rate monotonic period. Once initiated by the |
---|
[75e22db] | 722 | @code{@value{DIRPREFIX}rate_monotonic_period} directive, the period is |
---|
| 723 | said to run until it either expires or is reinitiated. The state of the rate |
---|
[ae68ff0] | 724 | monotonic period results in one of the following scenarios: |
---|
| 725 | |
---|
| 726 | @itemize @bullet |
---|
| 727 | @item If the rate monotonic period is running, the calling |
---|
| 728 | task will be blocked for the remainder of the outstanding period |
---|
| 729 | and, upon completion of that period, the period will be |
---|
| 730 | reinitiated with the specified period. |
---|
| 731 | |
---|
| 732 | @item If the rate monotonic period is not currently running |
---|
| 733 | and has not expired, it is initiated with a length of period |
---|
| 734 | ticks and the calling task returns immediately. |
---|
| 735 | |
---|
| 736 | @item If the rate monotonic period has expired before the task |
---|
[75e22db] | 737 | invokes the @code{@value{DIRPREFIX}rate_monotonic_period} directive, |
---|
| 738 | the period will be initiated with a length of period ticks and the calling task |
---|
[ae68ff0] | 739 | returns immediately with a timeout error status. |
---|
[75e22db] | 740 | |
---|
[ae68ff0] | 741 | @end itemize |
---|
| 742 | |
---|
[ed11cadf] | 743 | @subsection Obtaining the Status of a Period |
---|
[ae68ff0] | 744 | |
---|
[75e22db] | 745 | If the @code{@value{DIRPREFIX}rate_monotonic_period} directive is invoked |
---|
| 746 | with a period of @code{@value{RPREFIX}PERIOD_STATUS} ticks, the current |
---|
| 747 | state of the specified rate monotonic period will be returned. The following |
---|
[ae68ff0] | 748 | table details the relationship between the period's status and |
---|
[75e22db] | 749 | the directive status code returned by the |
---|
| 750 | @code{@value{DIRPREFIX}rate_monotonic_period} |
---|
[ae68ff0] | 751 | directive: |
---|
| 752 | |
---|
| 753 | @itemize @bullet |
---|
[f331481c] | 754 | @item @code{@value{RPREFIX}SUCCESSFUL} - period is running |
---|
[ae68ff0] | 755 | |
---|
[f331481c] | 756 | @item @code{@value{RPREFIX}TIMEOUT} - period has expired |
---|
[ae68ff0] | 757 | |
---|
[f331481c] | 758 | @item @code{@value{RPREFIX}NOT_DEFINED} - period has never been initiated |
---|
[ae68ff0] | 759 | @end itemize |
---|
| 760 | |
---|
| 761 | Obtaining the status of a rate monotonic period does |
---|
| 762 | not alter the state or length of that period. |
---|
| 763 | |
---|
| 764 | @subsection Canceling a Period |
---|
| 765 | |
---|
[75e22db] | 766 | The @code{@value{DIRPREFIX}rate_monotonic_cancel} directive is used to stop |
---|
[ae68ff0] | 767 | the period maintained by the specified rate monotonic period. |
---|
| 768 | The period is stopped and the rate monotonic period can be |
---|
[75e22db] | 769 | reinitiated using the @code{@value{DIRPREFIX}rate_monotonic_period} directive. |
---|
[ae68ff0] | 770 | |
---|
| 771 | @subsection Deleting a Rate Monotonic Period |
---|
| 772 | |
---|
[75e22db] | 773 | The @code{@value{DIRPREFIX}rate_monotonic_delete} directive is used to delete |
---|
[ae68ff0] | 774 | a rate monotonic period. If the period is running and has not |
---|
| 775 | expired, the period is automatically canceled. The rate |
---|
| 776 | monotonic period's control block is returned to the PCB free |
---|
| 777 | list when it is deleted. A rate monotonic period can be deleted |
---|
| 778 | by a task other than the task which created the period. |
---|
| 779 | |
---|
| 780 | @subsection Examples |
---|
| 781 | |
---|
| 782 | The following sections illustrate common uses of rate |
---|
| 783 | monotonic periods to construct periodic tasks. |
---|
| 784 | |
---|
| 785 | @subsection Simple Periodic Task |
---|
| 786 | |
---|
| 787 | This example consists of a single periodic task |
---|
| 788 | which, after initialization, executes every 100 clock ticks. |
---|
| 789 | |
---|
| 790 | @page |
---|
| 791 | @example |
---|
[5ab8aef] | 792 | rtems_task Periodic_task(rtems_task_argument arg) |
---|
[ae68ff0] | 793 | @{ |
---|
| 794 | rtems_name name; |
---|
| 795 | rtems_id period; |
---|
| 796 | rtems_status_code status; |
---|
| 797 | |
---|
[75e22db] | 798 | name = rtems_build_name( 'P', 'E', 'R', 'D' ); |
---|
[ae68ff0] | 799 | |
---|
[78287f41] | 800 | status = rtems_rate_monotonic_create( name, &period ); |
---|
[e3ec4cc] | 801 | if ( status != RTEMS_STATUS_SUCCESSFUL ) @{ |
---|
[3bee7f4] | 802 | printf( "rtems_monotonic_create failed with status of %d.\n", rc ); |
---|
| 803 | exit( 1 ); |
---|
[e3ec4cc] | 804 | @} |
---|
[3bee7f4] | 805 | |
---|
[ae68ff0] | 806 | |
---|
| 807 | while ( 1 ) @{ |
---|
[78287f41] | 808 | if ( rtems_rate_monotonic_period( period, 100 ) == RTEMS_TIMEOUT ) |
---|
[ae68ff0] | 809 | break; |
---|
| 810 | |
---|
| 811 | /* Perform some periodic actions */ |
---|
| 812 | @} |
---|
| 813 | |
---|
| 814 | /* missed period so delete period and SELF */ |
---|
| 815 | |
---|
[78287f41] | 816 | status = rtems_rate_monotonic_delete( period ); |
---|
[e3ec4cc] | 817 | if ( status != RTEMS_STATUS_SUCCESSFUL ) @{ |
---|
[78287f41] | 818 | printf( "rtems_rate_monotonic_delete failed with status of %d.\n", status ); |
---|
[3bee7f4] | 819 | exit( 1 ); |
---|
[e3ec4cc] | 820 | @} |
---|
[3bee7f4] | 821 | |
---|
| 822 | status = rtems_task_delete( SELF ); /* should not return */ |
---|
| 823 | printf( "rtems_task_delete returned with status of %d.\n", status ); |
---|
| 824 | exit( 1 ); |
---|
[ae68ff0] | 825 | @} |
---|
| 826 | @end example |
---|
| 827 | |
---|
| 828 | |
---|
| 829 | The above task creates a rate monotonic period as |
---|
| 830 | part of its initialization. The first time the loop is |
---|
[75e22db] | 831 | executed, the @code{@value{DIRPREFIX}rate_monotonic_period} |
---|
| 832 | directive will initiate the period for 100 ticks and return |
---|
| 833 | immediately. Subsequent invocations of the |
---|
| 834 | @code{@value{DIRPREFIX}rate_monotonic_period} directive will result |
---|
[ae68ff0] | 835 | in the task blocking for the remainder of the 100 tick period. |
---|
| 836 | If, for any reason, the body of the loop takes more than 100 |
---|
[75e22db] | 837 | ticks to execute, the @code{@value{DIRPREFIX}rate_monotonic_period} |
---|
| 838 | directive will return the @code{@value{RPREFIX}TIMEOUT} status. |
---|
| 839 | If the above task misses its deadline, it will delete the rate |
---|
| 840 | monotonic period and itself. |
---|
[ae68ff0] | 841 | |
---|
| 842 | @subsection Task with Multiple Periods |
---|
| 843 | |
---|
| 844 | This example consists of a single periodic task |
---|
| 845 | which, after initialization, performs two sets of actions every |
---|
| 846 | 100 clock ticks. The first set of actions is performed in the |
---|
| 847 | first forty clock ticks of every 100 clock ticks, while the |
---|
| 848 | second set of actions is performed between the fortieth and |
---|
| 849 | seventieth clock ticks. The last thirty clock ticks are not |
---|
| 850 | used by this task. |
---|
| 851 | |
---|
| 852 | @page |
---|
| 853 | @example |
---|
[5ab8aef] | 854 | rtems_task Periodic_task(rtems_task_argument arg) |
---|
[ae68ff0] | 855 | @{ |
---|
| 856 | rtems_name name_1, name_2; |
---|
| 857 | rtems_id period_1, period_2; |
---|
| 858 | rtems_status_code status; |
---|
| 859 | |
---|
[75e22db] | 860 | name_1 = rtems_build_name( 'P', 'E', 'R', '1' ); |
---|
| 861 | name_2 = rtems_build_name( 'P', 'E', 'R', '2' ); |
---|
[ae68ff0] | 862 | |
---|
[78287f41] | 863 | (void ) rtems_rate_monotonic_create( name_1, &period_1 ); |
---|
| 864 | (void ) rtems_rate_monotonic_create( name_2, &period_2 ); |
---|
[ae68ff0] | 865 | |
---|
| 866 | while ( 1 ) @{ |
---|
[78287f41] | 867 | if ( rtems_rate_monotonic_period( period_1, 100 ) == TIMEOUT ) |
---|
[ae68ff0] | 868 | break; |
---|
| 869 | |
---|
[78287f41] | 870 | if ( rtems_rate_monotonic_period( period_2, 40 ) == TIMEOUT ) |
---|
[ae68ff0] | 871 | break; |
---|
| 872 | |
---|
| 873 | /* |
---|
| 874 | * Perform first set of actions between clock |
---|
| 875 | * ticks 0 and 39 of every 100 ticks. |
---|
| 876 | */ |
---|
| 877 | |
---|
[78287f41] | 878 | if ( rtems_rate_monotonic_period( period_2, 30 ) == TIMEOUT ) |
---|
[ae68ff0] | 879 | break; |
---|
| 880 | |
---|
| 881 | /* |
---|
| 882 | * Perform second set of actions between clock 40 and 69 |
---|
| 883 | * of every 100 ticks. THEN ... |
---|
| 884 | * |
---|
| 885 | * Check to make sure we didn't miss the period_2 period. |
---|
| 886 | */ |
---|
| 887 | |
---|
[78287f41] | 888 | if ( rtems_rate_monotonic_period( period_2, STATUS ) == TIMEOUT ) |
---|
[ae68ff0] | 889 | break; |
---|
| 890 | |
---|
[78287f41] | 891 | (void) rtems_rate_monotonic_cancel( period_2 ); |
---|
[ae68ff0] | 892 | @} |
---|
| 893 | |
---|
| 894 | /* missed period so delete period and SELF */ |
---|
| 895 | |
---|
[78287f41] | 896 | (void ) rtems_rate_monotonic_delete( period_1 ); |
---|
| 897 | (void ) rtems_rate_monotonic_delete( period_2 ); |
---|
[ae68ff0] | 898 | (void ) task_delete( SELF ); |
---|
| 899 | @} |
---|
| 900 | @end example |
---|
| 901 | |
---|
| 902 | The above task creates two rate monotonic periods as |
---|
| 903 | part of its initialization. The first time the loop is |
---|
[75e22db] | 904 | executed, the @code{@value{DIRPREFIX}rate_monotonic_period} |
---|
| 905 | directive will initiate the period_1 period for 100 ticks |
---|
| 906 | and return immediately. Subsequent invocations of the |
---|
| 907 | @code{@value{DIRPREFIX}rate_monotonic_period} directive |
---|
[ae68ff0] | 908 | for period_1 will result in the task blocking for the remainder |
---|
| 909 | of the 100 tick period. The period_2 period is used to control |
---|
| 910 | the execution time of the two sets of actions within each 100 |
---|
[75e22db] | 911 | tick period established by period_1. The |
---|
| 912 | @code{@value{DIRPREFIX}rate_monotonic_cancel( period_2 )} |
---|
[5ab8aef] | 913 | call is performed to ensure that the period_2 period |
---|
[ae68ff0] | 914 | does not expire while the task is blocked on the period_1 |
---|
| 915 | period. If this cancel operation were not performed, every time |
---|
[5ab8aef] | 916 | the @code{@value{DIRPREFIX}rate_monotonic_period( period_2, 40 )} |
---|
[75e22db] | 917 | call is executed, except for the initial one, a directive status |
---|
| 918 | of @code{@value{RPREFIX}TIMEOUT} is returned. It is important to |
---|
[5ab8aef] | 919 | note that every time this call is made, the period_2 period will be |
---|
[75e22db] | 920 | initiated immediately and the task will not block. |
---|
[ae68ff0] | 921 | |
---|
| 922 | If, for any reason, the task misses any deadline, the |
---|
[75e22db] | 923 | @code{@value{DIRPREFIX}rate_monotonic_period} directive will |
---|
| 924 | return the @code{@value{RPREFIX}TIMEOUT} |
---|
[ae68ff0] | 925 | directive status. If the above task misses its deadline, it |
---|
| 926 | will delete the rate monotonic periods and itself. |
---|
| 927 | |
---|
| 928 | @section Directives |
---|
| 929 | |
---|
| 930 | This section details the rate monotonic manager's |
---|
| 931 | directives. A subsection is dedicated to each of this manager's |
---|
| 932 | directives and describes the calling sequence, related |
---|
| 933 | constants, usage, and status codes. |
---|
| 934 | |
---|
[169502e] | 935 | @c |
---|
| 936 | @c |
---|
| 937 | @c |
---|
[ae68ff0] | 938 | @page |
---|
| 939 | @subsection RATE_MONOTONIC_CREATE - Create a rate monotonic period |
---|
| 940 | |
---|
[169502e] | 941 | @cindex create a period |
---|
| 942 | |
---|
[ae68ff0] | 943 | @subheading CALLING SEQUENCE: |
---|
| 944 | |
---|
[61389eac] | 945 | @ifset is-C |
---|
[169502e] | 946 | @findex rtems_rate_monotonic_create |
---|
[ae68ff0] | 947 | @example |
---|
| 948 | rtems_status_code rtems_rate_monotonic_create( |
---|
| 949 | rtems_name name, |
---|
| 950 | rtems_id *id |
---|
| 951 | ); |
---|
| 952 | @end example |
---|
[61389eac] | 953 | @end ifset |
---|
| 954 | |
---|
| 955 | @ifset is-Ada |
---|
| 956 | @example |
---|
| 957 | procedure Rate_Monotonic_Create ( |
---|
| 958 | Name : in RTEMS.Name; |
---|
| 959 | ID : out RTEMS.ID; |
---|
| 960 | Result : out RTEMS.Status_Codes |
---|
| 961 | ); |
---|
| 962 | @end example |
---|
| 963 | @end ifset |
---|
[ae68ff0] | 964 | |
---|
| 965 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 966 | @code{@value{RPREFIX}SUCCESSFUL} - rate monotonic period created successfully@* |
---|
| 967 | @code{@value{RPREFIX}INVALID_NAME} - invalid task name@* |
---|
| 968 | @code{@value{RPREFIX}TOO_MANY} - too many periods created |
---|
[ae68ff0] | 969 | |
---|
| 970 | @subheading DESCRIPTION: |
---|
| 971 | |
---|
| 972 | This directive creates a rate monotonic period. The |
---|
| 973 | assigned rate monotonic id is returned in id. This id is used |
---|
| 974 | to access the period with other rate monotonic manager |
---|
| 975 | directives. For control and maintenance of the rate monotonic |
---|
| 976 | period, RTEMS allocates a PCB from the local PCB free pool and |
---|
| 977 | initializes it. |
---|
| 978 | |
---|
| 979 | @subheading NOTES: |
---|
| 980 | |
---|
| 981 | This directive will not cause the calling task to be |
---|
| 982 | preempted. |
---|
| 983 | |
---|
[169502e] | 984 | @c |
---|
| 985 | @c |
---|
| 986 | @c |
---|
[ae68ff0] | 987 | @page |
---|
| 988 | @subsection RATE_MONOTONIC_IDENT - Get ID of a period |
---|
| 989 | |
---|
[169502e] | 990 | @cindex get ID of a period |
---|
| 991 | @cindex obtain ID of a period |
---|
| 992 | |
---|
[ae68ff0] | 993 | @subheading CALLING SEQUENCE: |
---|
| 994 | |
---|
[61389eac] | 995 | @ifset is-C |
---|
[169502e] | 996 | @findex rtems_rate_monotonic_ident |
---|
[ae68ff0] | 997 | @example |
---|
| 998 | rtems_status_code rtems_rate_monotonic_ident( |
---|
| 999 | rtems_name name, |
---|
| 1000 | rtems_id *id |
---|
| 1001 | ); |
---|
| 1002 | @end example |
---|
[61389eac] | 1003 | @end ifset |
---|
| 1004 | |
---|
| 1005 | @ifset is-Ada |
---|
| 1006 | @example |
---|
| 1007 | procedure Rate_Monotonic_Ident ( |
---|
| 1008 | Name : in RTEMS.Name; |
---|
| 1009 | ID : out RTEMS.ID; |
---|
| 1010 | Result : out RTEMS.Status_Codes |
---|
| 1011 | ); |
---|
| 1012 | @end example |
---|
| 1013 | @end ifset |
---|
[ae68ff0] | 1014 | |
---|
| 1015 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 1016 | @code{@value{RPREFIX}SUCCESSFUL} - period identified successfully@* |
---|
| 1017 | @code{@value{RPREFIX}INVALID_NAME} - period name not found |
---|
[ae68ff0] | 1018 | |
---|
| 1019 | @subheading DESCRIPTION: |
---|
| 1020 | |
---|
| 1021 | This directive obtains the period id associated with |
---|
| 1022 | the period name to be acquired. If the period name is not |
---|
| 1023 | unique, then the period id will match one of the periods with |
---|
| 1024 | that name. However, this period id is not guaranteed to |
---|
| 1025 | correspond to the desired period. The period id is used to |
---|
| 1026 | access this period in other rate monotonic manager directives. |
---|
| 1027 | |
---|
| 1028 | @subheading NOTES: |
---|
| 1029 | |
---|
| 1030 | This directive will not cause the running task to be |
---|
| 1031 | preempted. |
---|
| 1032 | |
---|
[169502e] | 1033 | @c |
---|
| 1034 | @c |
---|
| 1035 | @c |
---|
[ae68ff0] | 1036 | @page |
---|
| 1037 | @subsection RATE_MONOTONIC_CANCEL - Cancel a period |
---|
| 1038 | |
---|
[169502e] | 1039 | @cindex cancel a period |
---|
| 1040 | |
---|
[ae68ff0] | 1041 | @subheading CALLING SEQUENCE: |
---|
| 1042 | |
---|
[61389eac] | 1043 | @ifset is-C |
---|
[169502e] | 1044 | @findex rtems_rate_monotonic_cancel |
---|
[ae68ff0] | 1045 | @example |
---|
| 1046 | rtems_status_code rtems_rate_monotonic_cancel( |
---|
| 1047 | rtems_id id |
---|
| 1048 | ); |
---|
| 1049 | @end example |
---|
[61389eac] | 1050 | @end ifset |
---|
| 1051 | |
---|
| 1052 | @ifset is-Ada |
---|
| 1053 | @example |
---|
| 1054 | procedure Rate_Monotonic_Cancel ( |
---|
| 1055 | ID : in RTEMS.ID; |
---|
| 1056 | Result : out RTEMS.Status_Codes |
---|
| 1057 | ); |
---|
| 1058 | @end example |
---|
| 1059 | @end ifset |
---|
[ae68ff0] | 1060 | |
---|
| 1061 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 1062 | @code{@value{RPREFIX}SUCCESSFUL} - period canceled successfully@* |
---|
| 1063 | @code{@value{RPREFIX}INVALID_ID} - invalid rate monotonic period id@* |
---|
| 1064 | @code{@value{RPREFIX}NOT_OWNER_OF_RESOURCE} - rate monotonic period not created by calling task |
---|
[ae68ff0] | 1065 | |
---|
| 1066 | @subheading DESCRIPTION: |
---|
| 1067 | |
---|
| 1068 | This directive cancels the rate monotonic period id. |
---|
| 1069 | This period will be reinitiated by the next invocation of |
---|
[75e22db] | 1070 | @code{@value{DIRPREFIX}rate_monotonic_period} with id. |
---|
[ae68ff0] | 1071 | |
---|
| 1072 | @subheading NOTES: |
---|
| 1073 | |
---|
| 1074 | This directive will not cause the running task to be |
---|
| 1075 | preempted. |
---|
| 1076 | |
---|
| 1077 | The rate monotonic period specified by id must have |
---|
| 1078 | been created by the calling task. |
---|
| 1079 | |
---|
[169502e] | 1080 | @c |
---|
| 1081 | @c |
---|
| 1082 | @c |
---|
[ae68ff0] | 1083 | @page |
---|
| 1084 | @subsection RATE_MONOTONIC_DELETE - Delete a rate monotonic period |
---|
| 1085 | |
---|
[169502e] | 1086 | @cindex delete a period |
---|
| 1087 | |
---|
[ae68ff0] | 1088 | @subheading CALLING SEQUENCE: |
---|
| 1089 | |
---|
[61389eac] | 1090 | @ifset is-C |
---|
[169502e] | 1091 | @findex rtems_rate_monotonic_delete |
---|
[ae68ff0] | 1092 | @example |
---|
| 1093 | rtems_status_code rtems_rate_monotonic_delete( |
---|
| 1094 | rtems_id id |
---|
| 1095 | ); |
---|
| 1096 | @end example |
---|
[61389eac] | 1097 | @end ifset |
---|
| 1098 | |
---|
| 1099 | @ifset is-Ada |
---|
| 1100 | @example |
---|
| 1101 | procedure Rate_Monotonic_Delete ( |
---|
| 1102 | ID : in RTEMS.ID; |
---|
| 1103 | Result : out RTEMS.Status_Codes |
---|
| 1104 | ); |
---|
| 1105 | @end example |
---|
| 1106 | @end ifset |
---|
[ae68ff0] | 1107 | |
---|
| 1108 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 1109 | @code{@value{RPREFIX}SUCCESSFUL} - period deleted successfully@* |
---|
| 1110 | @code{@value{RPREFIX}INVALID_ID} - invalid rate monotonic period id |
---|
[ae68ff0] | 1111 | |
---|
| 1112 | @subheading DESCRIPTION: |
---|
| 1113 | |
---|
| 1114 | This directive deletes the rate monotonic period |
---|
| 1115 | specified by id. If the period is running, it is automatically |
---|
| 1116 | canceled. The PCB for the deleted period is reclaimed by RTEMS. |
---|
| 1117 | |
---|
| 1118 | @subheading NOTES: |
---|
| 1119 | |
---|
| 1120 | This directive will not cause the running task to be |
---|
| 1121 | preempted. |
---|
| 1122 | |
---|
| 1123 | A rate monotonic period can be deleted by a task |
---|
| 1124 | other than the task which created the period. |
---|
| 1125 | |
---|
[169502e] | 1126 | @c |
---|
| 1127 | @c |
---|
| 1128 | @c |
---|
[ae68ff0] | 1129 | @page |
---|
| 1130 | @subsection RATE_MONOTONIC_PERIOD - Conclude current/Start next period |
---|
| 1131 | |
---|
[169502e] | 1132 | @cindex conclude current period |
---|
| 1133 | @cindex start current period |
---|
| 1134 | @cindex period initiation |
---|
| 1135 | |
---|
[ae68ff0] | 1136 | @subheading CALLING SEQUENCE: |
---|
| 1137 | |
---|
[61389eac] | 1138 | @ifset is-C |
---|
[169502e] | 1139 | @findex rtems_rate_monotonic_period |
---|
[ae68ff0] | 1140 | @example |
---|
| 1141 | rtems_status_code rtems_rate_monotonic_period( |
---|
| 1142 | rtems_id id, |
---|
| 1143 | rtems_interval length |
---|
| 1144 | ); |
---|
| 1145 | @end example |
---|
[61389eac] | 1146 | @end ifset |
---|
| 1147 | |
---|
| 1148 | @ifset is-Ada |
---|
| 1149 | @example |
---|
| 1150 | procedure Rate_Monotonic_Period ( |
---|
| 1151 | ID : in RTEMS.ID; |
---|
| 1152 | Length : in RTEMS.Interval; |
---|
| 1153 | Result : out RTEMS.Status_Codes |
---|
| 1154 | ); |
---|
| 1155 | @end example |
---|
| 1156 | @end ifset |
---|
[ae68ff0] | 1157 | |
---|
| 1158 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 1159 | @code{@value{RPREFIX}SUCCESSFUL} - period initiated successfully@* |
---|
| 1160 | @code{@value{RPREFIX}INVALID_ID} - invalid rate monotonic period id@* |
---|
| 1161 | @code{@value{RPREFIX}NOT_OWNER_OF_RESOURCE} - period not created by calling task@* |
---|
| 1162 | @code{@value{RPREFIX}NOT_DEFINED} - period has never been initiated (only |
---|
[cf5ef6d] | 1163 | possible when period is set to PERIOD_STATUS)@* |
---|
[f331481c] | 1164 | @code{@value{RPREFIX}TIMEOUT} - period has expired |
---|
[ae68ff0] | 1165 | |
---|
| 1166 | @subheading DESCRIPTION: |
---|
| 1167 | |
---|
| 1168 | This directive initiates the rate monotonic period id |
---|
| 1169 | with a length of period ticks. If id is running, then the |
---|
| 1170 | calling task will block for the remainder of the period before |
---|
| 1171 | reinitiating the period with the specified period. If id was |
---|
| 1172 | not running (either expired or never initiated), the period is |
---|
| 1173 | immediately initiated and the directive returns immediately. |
---|
| 1174 | |
---|
[f331481c] | 1175 | If invoked with a period of @code{@value{RPREFIX}PERIOD_STATUS} ticks, the |
---|
[ae68ff0] | 1176 | current state of id will be returned. The directive status |
---|
| 1177 | indicates the current state of the period. This does not alter |
---|
| 1178 | the state or period of the period. |
---|
| 1179 | |
---|
| 1180 | @subheading NOTES: |
---|
| 1181 | |
---|
| 1182 | This directive will not cause the running task to be preempted. |
---|
| 1183 | |
---|
[169502e] | 1184 | @c |
---|
| 1185 | @c |
---|
| 1186 | @c |
---|
[ae68ff0] | 1187 | @page |
---|
[35a81f8] | 1188 | @subsection RATE_MONOTONIC_GET_STATUS - Obtain status from a period |
---|
[ae68ff0] | 1189 | |
---|
[169502e] | 1190 | @cindex get status of period |
---|
| 1191 | @cindex obtain status of period |
---|
| 1192 | |
---|
[ae68ff0] | 1193 | @subheading CALLING SEQUENCE: |
---|
| 1194 | |
---|
[61389eac] | 1195 | @ifset is-C |
---|
[169502e] | 1196 | @findex rtems_rate_monotonic_get_status |
---|
[ae68ff0] | 1197 | @example |
---|
[61389eac] | 1198 | rtems_status_code rtems_rate_monotonic_get_status( |
---|
[ae68ff0] | 1199 | rtems_id id, |
---|
| 1200 | rtems_rate_monotonic_period_status *status |
---|
| 1201 | ); |
---|
| 1202 | @end example |
---|
[61389eac] | 1203 | @end ifset |
---|
| 1204 | |
---|
| 1205 | @ifset is-Ada |
---|
| 1206 | @example |
---|
| 1207 | procedure Rate_Monotonic_Get_Status ( |
---|
| 1208 | ID : in RTEMS.ID; |
---|
| 1209 | Status : out RTEMS.Rate_Monotonic_Period_Status; |
---|
| 1210 | Result : out RTEMS.Status_Codes |
---|
| 1211 | ); |
---|
| 1212 | @end example |
---|
| 1213 | @end ifset |
---|
[ae68ff0] | 1214 | |
---|
| 1215 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 1216 | @code{@value{RPREFIX}SUCCESSFUL} - period initiated successfully@* |
---|
| 1217 | @code{@value{RPREFIX}INVALID_ID} - invalid rate monotonic period id@* |
---|
| 1218 | @code{@value{RPREFIX}INVALID_ADDRESS} - invalid address of status@* |
---|
[ae68ff0] | 1219 | |
---|
| 1220 | @subheading DESCRIPTION: |
---|
| 1221 | |
---|
| 1222 | This directive returns status information associated with |
---|
[7e8a1fc] | 1223 | the rate monotonic period id in the following data @value{STRUCTURE}: |
---|
[ae68ff0] | 1224 | |
---|
[61389eac] | 1225 | @ifset is-C |
---|
[adee5979] | 1226 | @findex rtems_rate_monotonic_period_status |
---|
[ae68ff0] | 1227 | @example |
---|
| 1228 | typedef struct @{ |
---|
| 1229 | rtems_rate_monotonic_period_states state; |
---|
[adee5979] | 1230 | rtems_unsigned32 ticks_since_last_period; |
---|
| 1231 | rtems_unsigned32 ticks_executed_since_last_period; |
---|
[ae68ff0] | 1232 | @} rtems_rate_monotonic_period_status; |
---|
| 1233 | @end example |
---|
[61389eac] | 1234 | @end ifset |
---|
| 1235 | |
---|
| 1236 | @ifset is-Ada |
---|
| 1237 | @example |
---|
| 1238 | type Rate_Monotonic_Period_Status is |
---|
| 1239 | begin |
---|
[4ffbc49] | 1240 | State : RTEMS.Rate_Monotonic_Period_States; |
---|
| 1241 | Ticks_Since_Last_Period : RTEMS.Unsigned32; |
---|
[61389eac] | 1242 | Ticks_Executed_Since_Last_Period : RTEMS.Unsigned32; |
---|
| 1243 | end record; |
---|
| 1244 | @end example |
---|
| 1245 | @end ifset |
---|
[ae68ff0] | 1246 | |
---|
[75e22db] | 1247 | @c RATE_MONOTONIC_INACTIVE does not have RTEMS_ in front of it. |
---|
| 1248 | |
---|
[a94c5a5d] | 1249 | If the period's state is @code{RATE_MONOTONIC_INACTIVE}, both |
---|
[ae68ff0] | 1250 | ticks_since_last_period and ticks_executed_since_last_period |
---|
| 1251 | will be set to 0. Otherwise, ticks_since_last_period will |
---|
| 1252 | contain the number of clock ticks which have occurred since |
---|
[75e22db] | 1253 | the last invocation of the |
---|
| 1254 | @code{@value{DIRPREFIX}rate_monotonic_period} directive. |
---|
[ae68ff0] | 1255 | Also in this case, the ticks_executed_since_last_period will indicate |
---|
| 1256 | how much processor time the owning task has consumed since the invocation |
---|
[75e22db] | 1257 | of the @code{@value{DIRPREFIX}rate_monotonic_period} directive. |
---|
[ae68ff0] | 1258 | |
---|
| 1259 | @subheading NOTES: |
---|
| 1260 | |
---|
| 1261 | This directive will not cause the running task to be preempted. |
---|
[35a81f8] | 1262 | |
---|
| 1263 | @c |
---|
| 1264 | @c |
---|
| 1265 | @c |
---|
| 1266 | @page |
---|
| 1267 | @subsection RATE_MONOTONIC_GET_STATISTICS - Obtain statistics from a period |
---|
| 1268 | |
---|
| 1269 | @cindex get statistics of period |
---|
| 1270 | @cindex obtain statistics of period |
---|
| 1271 | |
---|
| 1272 | @subheading CALLING SEQUENCE: |
---|
| 1273 | |
---|
| 1274 | @ifset is-C |
---|
| 1275 | @findex rtems_rate_monotonic_get_statistics |
---|
| 1276 | @example |
---|
| 1277 | rtems_status_code rtems_rate_monotonic_get_statistics( |
---|
| 1278 | rtems_id id, |
---|
| 1279 | rtems_rate_monotonic_period_statistics *statistics |
---|
| 1280 | ); |
---|
| 1281 | @end example |
---|
| 1282 | @end ifset |
---|
| 1283 | |
---|
| 1284 | @ifset is-Ada |
---|
| 1285 | @example |
---|
[4ffbc49] | 1286 | NOT SUPPORTED FROM Ada BINDING |
---|
[35a81f8] | 1287 | @end example |
---|
| 1288 | @end ifset |
---|
| 1289 | |
---|
| 1290 | @subheading DIRECTIVE STATUS CODES: |
---|
| 1291 | @code{@value{RPREFIX}SUCCESSFUL} - period initiated successfully@* |
---|
| 1292 | @code{@value{RPREFIX}INVALID_ID} - invalid rate monotonic period id@* |
---|
| 1293 | @code{@value{RPREFIX}INVALID_ADDRESS} - invalid address of statistics@* |
---|
| 1294 | |
---|
| 1295 | @subheading DESCRIPTION: |
---|
| 1296 | |
---|
| 1297 | This directive returns statistics information associated with |
---|
| 1298 | the rate monotonic period id in the following data @value{STRUCTURE}: |
---|
| 1299 | |
---|
| 1300 | @ifset is-C |
---|
| 1301 | @findex rtems_rate_monotonic_period_statistics |
---|
| 1302 | @example |
---|
| 1303 | typedef struct @{ |
---|
| 1304 | uint32_t count; /* periods executed */ |
---|
| 1305 | uint32_t missed_count; /* period deadlines missed */ |
---|
| 1306 | uint32_t min_cpu_time; /* minimum CPU time used in a period */ |
---|
| 1307 | uint32_t max_cpu_time; /* maximum CPU time used in a period */ |
---|
| 1308 | uint32_t total_cpu_time; /* total CPU time consumed */ |
---|
| 1309 | uint32_t min_wall_time; /* minimum wall time used in a period */ |
---|
| 1310 | uint32_t max_wall_time; /* maximum wall time used in a period */ |
---|
| 1311 | uint32_t total_wall_time; /* total wall time consumed */ |
---|
| 1312 | @} rtems_rate_monotonic_period_statistics; |
---|
| 1313 | @end example |
---|
| 1314 | @end ifset |
---|
| 1315 | |
---|
| 1316 | @ifset is-Ada |
---|
| 1317 | @example |
---|
[4ffbc49] | 1318 | NOT SUPPORTED FROM Ada BINDING |
---|
[35a81f8] | 1319 | @end example |
---|
| 1320 | @end ifset |
---|
| 1321 | |
---|
| 1322 | This directive returns the current statistics information for |
---|
| 1323 | the period instance assocaited with @code{id}. The information |
---|
| 1324 | returned is indicated by the structure above. |
---|
| 1325 | |
---|
| 1326 | @subheading NOTES: |
---|
| 1327 | |
---|
| 1328 | This directive will not cause the running task to be preempted. |
---|
| 1329 | |
---|
| 1330 | @c |
---|
| 1331 | @c |
---|
| 1332 | @c |
---|
| 1333 | @page |
---|
| 1334 | @subsection RATE_MONOTONIC_RESET_STATISTICS - Reset statistics for a period |
---|
| 1335 | |
---|
| 1336 | @cindex reset statistics of period |
---|
| 1337 | |
---|
| 1338 | @subheading CALLING SEQUENCE: |
---|
| 1339 | |
---|
| 1340 | @ifset is-C |
---|
| 1341 | @findex rtems_rate_monotonic_reset_statistics |
---|
| 1342 | @example |
---|
| 1343 | rtems_status_code rtems_rate_monotonic_reset_statistics( |
---|
| 1344 | rtems_id id |
---|
| 1345 | ); |
---|
| 1346 | @end example |
---|
| 1347 | @end ifset |
---|
| 1348 | |
---|
| 1349 | @ifset is-Ada |
---|
| 1350 | @example |
---|
[4ffbc49] | 1351 | procedure Rate_Monotonic_Reset_Statistics ( |
---|
| 1352 | ID : in RTEMS.ID; |
---|
| 1353 | Result : out RTEMS.Status_Codes |
---|
| 1354 | ); |
---|
[35a81f8] | 1355 | @end example |
---|
| 1356 | @end ifset |
---|
| 1357 | |
---|
| 1358 | @subheading DIRECTIVE STATUS CODES: |
---|
| 1359 | @code{@value{RPREFIX}SUCCESSFUL} - period initiated successfully@* |
---|
| 1360 | @code{@value{RPREFIX}INVALID_ID} - invalid rate monotonic period id@* |
---|
| 1361 | |
---|
| 1362 | @subheading DESCRIPTION: |
---|
| 1363 | |
---|
| 1364 | This directive resets the statistics information associated with |
---|
| 1365 | this rate monotonic period instance. |
---|
| 1366 | |
---|
| 1367 | @subheading NOTES: |
---|
| 1368 | |
---|
| 1369 | This directive will not cause the running task to be preempted. |
---|
| 1370 | |
---|
| 1371 | @c |
---|
| 1372 | @c |
---|
| 1373 | @c |
---|
| 1374 | @page |
---|
| 1375 | @subsection RATE_MONOTONIC_RESET_ALL_STATISTICS - Reset statistics for all periods |
---|
| 1376 | |
---|
| 1377 | @cindex reset statistics of all periods |
---|
| 1378 | |
---|
| 1379 | @subheading CALLING SEQUENCE: |
---|
| 1380 | |
---|
| 1381 | @ifset is-C |
---|
| 1382 | @findex rtems_rate_monotonic_reset_all_statistics |
---|
| 1383 | @example |
---|
| 1384 | void rtems_rate_monotonic_reset_all_statistics(void); |
---|
| 1385 | @end example |
---|
| 1386 | @end ifset |
---|
| 1387 | |
---|
| 1388 | @ifset is-Ada |
---|
| 1389 | @example |
---|
[4ffbc49] | 1390 | procedure Rate_Monotonic_Reset_All_Statistics; |
---|
[35a81f8] | 1391 | @end example |
---|
| 1392 | @end ifset |
---|
| 1393 | |
---|
| 1394 | @subheading DIRECTIVE STATUS CODES: |
---|
| 1395 | |
---|
| 1396 | NONE |
---|
| 1397 | |
---|
| 1398 | @subheading DESCRIPTION: |
---|
| 1399 | |
---|
| 1400 | This directive resets the statistics information associated with |
---|
| 1401 | all rate monotonic period instances. |
---|
| 1402 | |
---|
| 1403 | @subheading NOTES: |
---|
| 1404 | |
---|
| 1405 | This directive will not cause the running task to be preempted. |
---|
| 1406 | |
---|
| 1407 | @c |
---|
| 1408 | @c |
---|
| 1409 | @c |
---|
| 1410 | @page |
---|
| 1411 | @subsection RATE_MONOTONIC_REPORT_STATISTICS - Print period statistics report |
---|
| 1412 | |
---|
| 1413 | @cindex print period statistics report |
---|
| 1414 | @cindex period statistics report |
---|
| 1415 | |
---|
| 1416 | @subheading CALLING SEQUENCE: |
---|
| 1417 | |
---|
| 1418 | @ifset is-C |
---|
| 1419 | @findex rtems_rate_monotonic_report_statistics |
---|
| 1420 | @example |
---|
| 1421 | void rtems_rate_monotonic_report_statistics(void); |
---|
| 1422 | @end example |
---|
| 1423 | @end ifset |
---|
| 1424 | |
---|
| 1425 | @ifset is-Ada |
---|
| 1426 | @example |
---|
[4ffbc49] | 1427 | procedure Rate_Monotonic_Report_Statistics; |
---|
[35a81f8] | 1428 | @end example |
---|
| 1429 | @end ifset |
---|
| 1430 | |
---|
| 1431 | @subheading DIRECTIVE STATUS CODES: |
---|
| 1432 | |
---|
| 1433 | NONE |
---|
| 1434 | |
---|
| 1435 | @subheading DESCRIPTION: |
---|
| 1436 | |
---|
| 1437 | This directive prints a report on all active periods which have |
---|
| 1438 | executed at least one period. The following is an example of the |
---|
| 1439 | output generated by this directive. |
---|
| 1440 | |
---|
| 1441 | @ifset is-C |
---|
| 1442 | @findex rtems_rate_monotonic_period_statistics |
---|
| 1443 | @example |
---|
| 1444 | ID OWNER PERIODS MISSED CPU TIME WALL TIME |
---|
[76b839b] | 1445 | MIN/MAX/AVG MIN/MAX/AVG |
---|
[35a81f8] | 1446 | 0x42010001 TA1 502 0 0/1/0.99 0/0/0.00 |
---|
| 1447 | 0x42010002 TA2 502 0 0/1/0.99 0/0/0.00 |
---|
| 1448 | 0x42010003 TA3 501 0 0/1/0.99 0/0/0.00 |
---|
| 1449 | 0x42010004 TA4 501 0 0/1/0.99 0/0/0.00 |
---|
| 1450 | 0x42010005 TA5 10 0 0/1/0.90 0/0/0.00 |
---|
| 1451 | @end example |
---|
| 1452 | @end ifset |
---|
| 1453 | |
---|
| 1454 | @subheading NOTES: |
---|
| 1455 | |
---|
| 1456 | This directive will not cause the running task to be preempted. |
---|