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2010-11-24 Gedare Bloom <giddyup44@yahoo.com>

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PR 1647/cpukit
	* user/conf.t, user/schedule.t: Update documentation to reflect
	refactoring of SuperCore to add Scheduler and ability for user to
	configure a scheduler.
This commit is contained in:
Joel Sherrill
2010-11-24 15:52:21 +00:00
parent 0faa9dad07
commit db9964f185
3 changed files with 113 additions and 2 deletions
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7
doc/ChangeLog
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@@ -1,3 +1,10 @@
2010-11-24 Gedare Bloom <giddyup44@yahoo.com>
PR 1647/cpukit
* user/conf.t, user/schedule.t: Update documentation to reflect
refactoring of SuperCore to add Scheduler and ability for user to
configure a scheduler.
2010-11-11 Joel Sherrill <joel.sherrilL@OARcorp.com>
PR 1716/doc

56
doc/user/conf.t
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@@ -24,6 +24,7 @@ RTEMS must be configured for an application. This configuration
information encompasses a variety of information including
the length of each clock tick, the maximum number of each RTEMS
object that can be created, the application initialization tasks,
the task scheduling algorithm to be used,
and the device drivers in the application. This information
is placed in data structures that are given to RTEMS at
system initialization time. This chapter details the
@@ -389,6 +390,54 @@ and the user is assumed to provide one or more initialization tasks.
@end itemize
@c
@c
@c
@subsection Scheduler Algorithm Configuration
This section defines the configuration parameters related to selecting
a scheduling algorithm for an application. Regardless of whether
@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
@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
@item @code{CONFIGURE_SCHEDULER_PRIORITY} is defined if the application
will use the Priority Scheduling algorithm.
If none of the previous configuration parameters are defined by the
application, then @code{rtems/confdefs.h} will define
@code{CONFIGURE_SCHEDULER_POLICY} as @code{_Scheduler_PRIORITY}.
@end itemize
@c
@c
@c
@@ -816,6 +865,7 @@ typedef struct @{
uint32_t maximum_extensions;
uint32_t microseconds_per_tick;
uint32_t ticks_per_timeslice;
uint32_t scheduler_policy;
void (*idle_task)( void );
uint32_t idle_task_stack_size;
uint32_t interrupt_stack_size;
@@ -875,6 +925,12 @@ When using the @code{rtems/confdefs.h} mechanism for configuring
an RTEMS application, the value for this field corresponds
to the setting of the macro @code{CONFIGURE_TICKS_PER_TIMESLICE}.
@item scheduler_policy
is the algorithm to use for task scheduling.
When using the @code{rtems/confdefs.h} mechanism for configuring
an RTEMS application, the value for this field corresponds
to the setting of the macro @code{CONFIGURE_SCHEDULER_POLICY}.
@item idle_task
is the address of the optional user
provided routine which is used as the system's IDLE task. If

52
doc/user/schedule.t
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@@ -30,7 +30,30 @@ The component of RTEMS responsible for providing this
capability is appropriately called the scheduler. The
scheduler's sole purpose is to allocate the all important
resource of processor time to the various tasks competing for
attention. The RTEMS scheduler allocates the processor using a
attention.
@section Scheduling Algorithms
@cindex scheduling algorithms
RTEMS provides multiple possible scheduling algorithms, each
of which are appropriate to different use case scenarios.
The classic RTEMS scheduling algorithm -- the only
algorithm available in RTEMS 4.10 and earlier -- is the priority
scheduling algorithm. When not specified, the priority scheduling
algorithm can be assumed.
RTEMS currently supports the following scheduling algorithms:
@itemize @bullet
@item Priority scheduling
@end itemize
@subsection Priority Scheduling
@cindex priority scheduling
The RTEMS scheduler allocates the processor using a
priority-based, preemptive algorithm augmented to provide
round-robin characteristics within individual priority groups.
The goal of this algorithm is to guarantee that the task which
@@ -50,6 +73,11 @@ chain is allocated the processor. RTEMS schedules tasks using
the second method to guarantee faster response times to external
events.
Priority scheduling is the most commonly used scheduling algorithm.
It should be used by applications in which multiple tasks contend for
CPU time or other resources and there is a need to ensure certain tasks
are given priority over other tasks.
@section Scheduling Mechanisms
@cindex scheduling mechanisms
@@ -81,6 +109,11 @@ description.
@cindex task priority
This mechanism affects the following scheduling algorithms:
@itemize @bullet
@item Priority scheduling
@end itemize
The most significant of these mechanisms is the
ability for the user to assign a priority level to each
individual task when it is created and to alter a task's
@@ -104,6 +137,11 @@ to a task.}
@cindex preemption
This mechanism affects the following scheduling algorithms:
@itemize @bullet
@item Priority scheduling
@end itemize
Another way the user can alter the basic scheduling
algorithm is by manipulating the preemption mode flag
(@code{@value{RPREFIX}PREEMPT_MASK}) of individual tasks. If preemption is disabled
@@ -120,6 +158,11 @@ control of the processor.
@cindex timeslicing
@cindex round robin scheduling
This mechanism affects the following scheduling algorithms:
@itemize @bullet
@item Priority scheduling
@end itemize
Timeslicing or round-robin scheduling is an
additional method which can be used to alter the basic
scheduling algorithm. Like preemption, timeslicing is specified
@@ -141,6 +184,11 @@ entire timeslice.
@cindex manual round robin
This mechanism affects the following scheduling algorithms:
@itemize @bullet
@item Priority scheduling
@end itemize
The final mechanism for altering the RTEMS scheduling
algorithm is called manual round-robin. Manual round-robin is
invoked by using the @code{@value{DIRPREFIX}task_wake_after}
@@ -151,7 +199,7 @@ end of its priority group. If no other tasks of the same
priority are ready to run, then the task does not lose control
of the processor.
@subsection Dispatching Tasks
@section Dispatching Tasks
@cindex dispatching