[Xenomai-help] no-brainer realtime issue

2006-02-16 Thread Steven Seeger 
I have a xenomai userspace application that does the following:

A thread of priority 90 toggles a bit (outb) to move a stepper motor.

A thread of priority 10 updates the display once a second.

The motor thread is periodic and uses rt_task_wait_period(). The display
thread just uses sleep(1).

My question is this: the priority 90 thread is higher priority, and doesn't
do anything relating to linux system calls. Whenever the display thread
updates the display, the motor thread stalls momentarily.

Any idea why this is?

Steven


___
Xenomai-help mailing list
Xenomai-help@gna.org
https://mail.gna.org/listinfo/xenomai-help

Re: [Xenomai-help] no-brainer realtime issue

2006-02-16 Thread Jan Kiszka 
Steven Seeger wrote:
 I have a xenomai userspace application that does the following:
 
 A thread of priority 90 toggles a bit (outb) to move a stepper motor.
 
 A thread of priority 10 updates the display once a second.
 
 The motor thread is periodic and uses rt_task_wait_period(). The display
 thread just uses sleep(1).
 
 My question is this: the priority 90 thread is higher priority, and doesn't
 do anything relating to linux system calls. Whenever the display thread
 updates the display, the motor thread stalls momentarily.
 
 Any idea why this is?

If your motor thread really looks like

while (1) {
toggle_bit();
rt_task_wait_period();
}

you may suffer from contentions of the related bus towards your motor
(what kind of interface do you use?).

To test this, just put some instrumentation around the toggle_bit()
(take timestamps and look for abnormal delays). What frequency is your
motor thread running at?

If there is more code in your loop, please post the program (or a
simplified but still failing version).

Jan



signature.asc
Description: OpenPGP digital signature
___
Xenomai-help mailing list
Xenomai-help@gna.org
https://mail.gna.org/listinfo/xenomai-help

Re: [Xenomai-help] no-brainer realtime issue

2006-02-16 Thread Philippe Gerum 

Jan Kiszka wrote:

Steven Seeger wrote:


I have a xenomai userspace application that does the following:

A thread of priority 90 toggles a bit (outb) to move a stepper motor.

A thread of priority 10 updates the display once a second.

The motor thread is periodic and uses rt_task_wait_period(). The display
thread just uses sleep(1).

My question is this: the priority 90 thread is higher priority, and doesn't
do anything relating to linux system calls. Whenever the display thread
updates the display, the motor thread stalls momentarily.

Any idea why this is?



If your motor thread really looks like

while (1) {
toggle_bit();
rt_task_wait_period();
}

you may suffer from contentions of the related bus towards your motor
(what kind of interface do you use?).

To test this, just put some instrumentation around the toggle_bit()
(take timestamps and look for abnormal delays). What frequency is your
motor thread running at?

If there is more code in your loop, please post the program (or a
simplified but still failing version).


Additionally, the output of /proc/xenomai/stat for a failing run might give some 
useful information.




Jan





___
Xenomai-help mailing list
Xenomai-help@gna.org
https://mail.gna.org/listinfo/xenomai-help



--

Philippe.

___
Xenomai-help mailing list
Xenomai-help@gna.org
https://mail.gna.org/listinfo/xenomai-help