On 2014-04-10 04:27, Chris Johns wrote:
The short circuit logic for non-smp should be in the api level code
and the
score should have NO code for affinity.
Since the affinity support is used by the Classic and POSIX API it must
stay in the score.
Conditionally removed on uniprocessor builds ?
Otherwise you impact the minimum profile and this is 100% unacceptable.
There is no overhead in the non-SMP configurations if you don't use the
task set/get affinity functions. The scheduler get/set affinity
operations are only available in SMP configurations.
Could you please elaborate ? If I do not use the functions the score includes
no extra code related to this API, ie the scope is limited to the API layer ?
Lets look at rtems_task_get_affinity() for example. This function makes sense
on a uni-processor system since this can be viewed as an SMP system with only
one processor. The implementation is like this:
rtems_status_code rtems_task_get_affinity(
rtems_id id,
size_t cpusetsize,
cpu_set_t *cpuset
)
{
Thread_Control *the_thread;
Objects_Locations location;
bool ok;
if ( !cpuset )
return RTEMS_INVALID_ADDRESS;
the_thread = _Thread_Get( id, &location );
switch ( location ) {
case OBJECTS_LOCAL:
ok = _Scheduler_Get_affinity(
_Scheduler_Get( the_thread ),
the_thread,
cpusetsize,
cpuset
);
_Objects_Put( &the_thread->Object );
return ok ? RTEMS_SUCCESSFUL : RTEMS_INVALID_NUMBER;
#if defined(RTEMS_MULTIPROCESSING)
case OBJECTS_REMOTE:
#endif
case OBJECTS_ERROR:
break;
}
return RTEMS_INVALID_ID;
}
This leads to _Scheduler_Get_affinity():
bool _Scheduler_Get_affinity(
const Scheduler_Control *scheduler,
Thread_Control *the_thread,
size_t cpusetsize,
cpu_set_t *cpuset
)
{
bool ok;
if ( _CPU_set_Is_large_enough( cpusetsize ) ) {
#if defined(RTEMS_SMP)
ok = ( *scheduler->Operations.get_affinity )(
scheduler,
the_thread,
cpusetsize,
cpuset
);
#else
ok = _Scheduler_default_Get_affinity_body(
scheduler,
the_thread,
cpusetsize,
cpuset
);
#endif
} else {
ok = false;
}
return ok;
}
On non-SMP this leads to _Scheduler_default_Get_affinity_body(). Please note
that we have no get/set affinity operation!
RTEMS_INLINE_ROUTINE bool _Scheduler_default_Get_affinity_body(
const Scheduler_Control *scheduler,
Thread_Control *the_thread,
size_t cpusetsize,
cpu_set_t *cpuset
)
{
uint32_t cpu_count = _SMP_Get_processor_count();
uint32_t cpu_index;
(void) scheduler;
(void) the_thread;
CPU_ZERO_S( cpusetsize, cpuset );
for ( cpu_index = 0 ; cpu_index < cpu_count ; ++cpu_index ) {
CPU_SET_S( (int) cpu_index, cpusetsize, cpuset );
}
return true;
}
On non-SMP _SMP_Get_processor_count() is a compile-time constant of one.
So if you use rtems_task_get_affinity() on non-SMP you have of course the
overhead for this function to return a cpuset with all bits except bit 0 set to
zero. You have no overhead in the rest of the system, e.g. not set/get
affinity operations in the scheduler, global variables, structure variables, etc.
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.hu...@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
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