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2011-02-17 Joel Sherrill <joel.sherrill@oarcorp.com>

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* user/conf.t: Document changes to Scheduler configuration.
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Joel Sherrill
2011-02-17 22:37:06 +00:00
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doc/ChangeLog
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@@ -1,3 +1,7 @@
2011-02-17 Joel Sherrill <joel.sherrill@oarcorp.com>
* user/conf.t: Document changes to Scheduler configuration.
2011-02-02 Ralf Corsépius <ralf.corsepius@rtems.org> 2011-02-02 Ralf Corsépius <ralf.corsepius@rtems.org>
* configure.ac: Require autoconf-2.68, automake-1.11.1. * configure.ac: Require autoconf-2.68, automake-1.11.1.

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doc/user/conf.t
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@@ -394,50 +394,52 @@ and the user is assumed to provide one or more initialization tasks.
@c @c
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@subsection Scheduler Algorithm Configuration @subsection Scheduler Algorithm Configuration
This section defines the configuration parameters related to selecting This section defines the configuration parameters related to selecting
a scheduling algorithm for an application. Regardless of whether a scheduling algorithm for an application. For the schedulers built into RTEMS, the configuration is straightforward. All that is required is to define the configuration macro which specifies which scheduler you want for in your application. The currently available schedulers are:
@code{CONFIGURE_SCHEDULER_POLICY} is defined, if none of the other
configuration parameters are set, then @code{rtems/confdefs.h} will define
@code{CONFIGURE_SCHEDULER_PRIORITY} and will (re)define
@code{CONFIGURE_SCHEDULER_POLICY} as @code{_Scheduler_Priority}. That is,
@code{CONFIGURE_SCHEDULER_PRIORITY} is the default scheduling algorithm.
@itemize @bullet @itemize @bullet
@findex CONFIGURE_SCHEDULER_POLICY
@item @code{CONFIGURE_SCHEDULER_POLICY} is defined to specify which
scheduling algorithm an application will use. If it is undefined,
then @code{rtems/confdefs.h} will define it based on the definition
of the following configuration parameters.
Valid values for this configuration parameter are:
@code{_Scheduler_USER},
@code{_Scheduler_Priority}.
@findex CONFIGURE_SCHEDULER_USER
@item @code{CONFIGURE_SCHEDULER_USER} is defined if the application
provides its own scheduling algorithm. If @code{CONFIGURE_SCHEDULER_USER} is
defined then @code{CONFIGURE_SCHEDULER_ENTRY_USER} must be defined with the
name of the application's initialization function. If both
configuration parameters are defined and @code{CONFIGURE_SCHEDULER_POLICY}
is undefined, then @code{CONFIGURE_SCHEDULER_POLICY} will be be defined as
@code{_Scheduler_USER}.
@findex CONFIGURE_SCHEDULER_ALL
@item @code{CONFIGURE_SCHEDULER_ALL} is defined if the application
chooses to include all of the RTEMS-provided schedulers.
@code{CONFIGURE_SCHEDULER_ALL} will define all of the following configuration
parameters and will use @code{CONFIGURE_SCHEDULER_POLICY} to select the
algorithm to use. If @code{CONFIGURE_SCHEDULER_POLICY} is not defined, then
@code{rtems/confdefs.h} will define it as @code{_Scheduler_Priority}.
@findex CONFIGURE_SCHEDULER_PRIORITY @findex CONFIGURE_SCHEDULER_PRIORITY
@item @code{CONFIGURE_SCHEDULER_PRIORITY} is defined if the application @item Deterministic Priority Scheduler - This is the default scheduler
will use the Priority Scheduling algorithm. in RTEMS and is designed for predictable performance under the highest
If none of the previous configuration parameters are defined by the loads. It can block or unblock a thread in a constant amount of time.
application, then @code{rtems/confdefs.h} will define This scheduler requires a variable amount of memory based upon the number
@code{CONFIGURE_SCHEDULER_POLICY} as @code{_Scheduler_PRIORITY}. of priorities configured in the system. This scheduler may be explicitly
selected by defining @code{CONFIGURE_SCHEDULER_PRIORITY}.
@end itemize @end itemize
The pluggable scheduler interface was added after the 4.10 release series
so there are not a lot of options at this point. We anticipate a lower
memory, non-deterministic priority scheduler suitable for use in small
systems and an Earliest Deadline First Scheduler (EDF) to arrive in
the future.
The pluggable scheduler interface enables the user to provide their own scheduling algorithm. If you choose to do this, you must define multiple configuration macros.
@findex CONFIGURE_SCHEDULER_USER
First, you must define @code{CONFIGURE_SCHEDULER_USER} to indicate the application provides its own scheduling algorithm. If @code{CONFIGURE_SCHEDULER_USER} is defined then the following additional macros must be defined:
@itemize @bullet
@item @code{CONFIGURE_SCHEDULER_USER_ENTRY_POINTS} must be defined with the set of methods which implement this scheduler.
@item @code{CONFIGURE_MEMORY_FOR_SCHEDULER} must be defined with the
amount of memory required as a base amount for the scheduler.
@item @code{CONFIGURE_MEMORY_PER_TASK_FOR_SCHEDULER(_tasks)} must be
defined as a formula which computes the amount of memory required based upon the number of tasks configured.
@end itemize
At this time, the mechanics and requirements for writing a new
scheduler are evolving and not fully documented. It is recommended
that you look at the existing Deterministic Priority Scheduler
in @code{cpukit/score/src/schedulerpriority*.c} for guidance.
For guidance on the configuration macros, please examine
@code{cpukit/sapi/include/confdefs.h} for how these are defined for the
Deterministic Priority Scheduler.
@c @c
@c @c
@c @c