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143 lines
3.5 KiB
Perl
143 lines
3.5 KiB
Perl
@c
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@c COPYRIGHT (c) 1988-2002.
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@c On-Line Applications Research Corporation (OAR).
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@c All rights reserved.
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@c
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@c $Id$
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@c
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@chapter CPU Usage Statistics
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@section Introduction
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The CPU usage statistics manager is an RTEMS support
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component that provides a convenient way to manipulate
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the CPU usage information associated with each task
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The routines provided by the CPU usage statistics manager are:
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@itemize @bullet
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@item @code{CPU_usage_Dump} - Report CPU Usage Statistics
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@item @code{CPU_usage_Reset} - Reset CPU Usage Statistics
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@end itemize
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@section Background
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@section Operations
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@section Report CPU Usage Statistics
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@subsection Reporting Period Statistics
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The application may dynamically report the CPU usage for every
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task in the system by calling the @code{CPU_usage_Dump} routine.
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This routine prints a table with the following information per task:
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@itemize @bullet
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@item task id
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@item task name
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@item number of clock ticks executed
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@item percentage of time consumed by this task
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@end itemize
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The following is an example of the report generated:
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@example
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@group
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CPU Usage by thread
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ID NAME TICKS PERCENT
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0x04010001 IDLE 0 0.000
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0x08010002 TA1 1203 0.748
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0x08010003 TA2 203 0.126
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0x08010004 TA3 202 0.126
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Ticks since last reset = 1600
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Total Units = 1608
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@end group
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@end example
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Notice that the "Total Units" is greater than the ticks per reset.
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This is an artifact of the way in which RTEMS keeps track of CPU
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usage. When a task is context switched into the CPU, the number
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of clock ticks it has executed is incremented. While the task
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is executing, this number is incremented on each clock tick.
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Otherwise, if a task begins and completes execution between
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successive clock ticks, there would be no way to tell that it
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executed at all.
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Another thing to keep in mind when looking at idle time, is that
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many systems -- especially during debug -- have a task providing
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some type of debug interface. It is usually fine to think of the
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total idle time as being the sum of the IDLE task and a debug
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task that will not be included in a production build of an application.
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@section Reset CPU Usage Statistics
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Invoking the @code{CPU_usage_Reset} routine resets the CPU usage
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statistics for all tasks in the system.
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@section Directives
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This section details the CPU usage statistics manager's directives.
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A subsection is dedicated to each of this manager's directives
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and describes the calling sequence, related constants, usage,
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and status codes.
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@page
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@subsection CPU_usage_Dump - Report CPU Usage Statistics
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@subheading CALLING SEQUENCE:
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@ifset is-C
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@example
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void CPU_usage_Dump( void );
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@end example
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@end ifset
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@ifset is-Ada
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@example
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An Ada interface is not currently available.
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@end example
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@end ifset
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@subheading STATUS CODES: NONE
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@subheading DESCRIPTION:
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This routine prints out a table detailing the CPU usage statistics for
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all tasks in the system.
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@subheading NOTES:
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NONE
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@page
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@subsection CPU_usage_Reset - Reset CPU Usage Statistics
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@subheading CALLING SEQUENCE:
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@ifset is-C
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@example
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void CPU_usage_Reset( void );
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@end example
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@end ifset
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@ifset is-Ada
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@example
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An Ada interface is not currently available.
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@end example
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@end ifset
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@subheading STATUS CODES: NONE
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@subheading DESCRIPTION:
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This routine re-initializes the CPU usage statistics for all tasks
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in the system to their initial state. The initial state is that
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a task has not executed and thus has consumed no CPU time.
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default state which is when zero period executions have occurred.
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@subheading NOTES:
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NONE
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