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-@c
-@c COPYRIGHT (c) 1988-2007.
-@c On-Line Applications Research Corporation (OAR).
-@c All rights reserved.
-
-@chapter CPU Usage Statistics
-
-@section Introduction
-
-The CPU usage statistics manager is an RTEMS support
-component that provides a convenient way to manipulate
-the CPU usage information associated with each task
-The routines provided by the CPU usage statistics manager are:
-
-@itemize @bullet
-@item @code{@value{DIRPREFIX}cpu_usage_report} - Report CPU Usage Statistics
-@item @code{@value{DIRPREFIX}cpu_usage_reset} - Reset CPU Usage Statistics
-@end itemize
-
-@section Background
-
-When analyzing and debugging real-time applications, it is important
-to be able to know how much CPU time each task in the system consumes.
-This support component provides a mechanism to easily obtain this
-information with little burden placed on the target.
-
-The raw data is gathered as part of performing a context switch. RTEMS
-keeps track of how many clock ticks have occurred which the task being
-switched out has been executing. If the task has been running less than
-1 clock tick, then for the purposes of the statistics, it is assumed to
-have executed 1 clock tick. This results in some inaccuracy but the
-alternative is for the task to have appeared to execute 0 clock ticks.
-
-RTEMS versions newer than the 4.7 release series, support the ability
-to obtain timestamps with nanosecond granularity if the BSP provides
-support. It is a desirable enhancement to change the way the usage
-data is gathered to take advantage of this recently added capability.
-Please consider sponsoring the core RTEMS development team to add
-this capability.
-
-@section Operations
-
-@subsection Report CPU Usage Statistics
-
-The application may dynamically report the CPU usage for every
-task in the system by calling the
-@code{@value{DIRPREFIX}cpu_usage_report} routine.
-This routine prints a table with the following information per task:
-
-@itemize @bullet
-@item task id
-@item task name
-@item number of clock ticks executed
-@item percentage of time consumed by this task
-@end itemize
-
-The following is an example of the report generated:
-
-@smallexample
-@group
--------------------------------------------------------------------------------
- CPU USAGE BY THREAD
-------------+----------------------------------------+---------------+---------
- ID | NAME | SECONDS | PERCENT
-------------+----------------------------------------+---------------+---------
- 0x04010001 | IDLE | 0 | 0.000
- 0x08010002 | TA1 | 1203 | 0.748
- 0x08010003 | TA2 | 203 | 0.126
- 0x08010004 | TA3 | 202 | 0.126
-------------+----------------------------------------+---------------+---------
- TICKS SINCE LAST SYSTEM RESET: 1600
- TOTAL UNITS: 1608
--------------------------------------------------------------------------------
-@end group
-@end smallexample
-
-Notice that the "TOTAL UNITS" is greater than the ticks per reset.
-This is an artifact of the way in which RTEMS keeps track of CPU
-usage. When a task is context switched into the CPU, the number
-of clock ticks it has executed is incremented. While the task
-is executing, this number is incremented on each clock tick.
-Otherwise, if a task begins and completes execution between
-successive clock ticks, there would be no way to tell that it
-executed at all.
-
-Another thing to keep in mind when looking at idle time, is that
-many systems -- especially during debug -- have a task providing
-some type of debug interface. It is usually fine to think of the
-total idle time as being the sum of the IDLE task and a debug
-task that will not be included in a production build of an application.
-
-@subsection Reset CPU Usage Statistics
-
-Invoking the @code{@value{DIRPREFIX}cpu_usage_reset} routine resets
-the CPU usage statistics for all tasks in the system.
-
-@section Directives
-
-This section details the CPU usage statistics manager's directives.
-A subsection is dedicated to each of this manager's directives
-and describes the calling sequence, related constants, usage,
-and status codes.
-
-@page
-@subsection cpu_usage_report - Report CPU Usage Statistics
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-void rtems_cpu_usage_report( void );
-@end example
-@end ifset
-
-@ifset is-Ada
-@example
-procedure CPU_Usage_Report;
-@end example
-@end ifset
-
-@subheading STATUS CODES: NONE
-
-@subheading DESCRIPTION:
-
-This routine prints out a table detailing the CPU usage statistics for
-all tasks in the system.
-
-@subheading NOTES:
-
-The table is printed using the @code{printk} routine.
-
-@page
-@subsection cpu_usage_reset - Reset CPU Usage Statistics
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-void rtems_cpu_usage_reset( void );
-@end example
-@end ifset
-
-@ifset is-Ada
-@example
-procedure CPU_Usage_Reset;
-@end example
-@end ifset
-
-@subheading STATUS CODES: NONE
-
-@subheading DESCRIPTION:
-
-This routine re-initializes the CPU usage statistics for all tasks
-in the system to their initial state. The initial state is that
-a task has not executed and thus has consumed no CPU time.
-default state which is when zero period executions have occurred.
-
-@subheading NOTES:
-
-NONE