[Xenomai-help] Time between ISR and RT Task

[Xenomai-help] Time between ISR and RT Task

[GSM909]

Hello

I have run a few programs with Xenomai tasks and have no problems. But I notice that the time between ISR and RT task ( RT task is suspended and resumed by the ISR) is shorter when Linux have a lot of work ( average load around 10 ) as when Linux has nothing to do( al : 0.05 ). 

My simple Question is why ?? :) 

thx 
Ted
-- 


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Re: [Xenomai-help] Time between ISR and RT Task

[Gilles Chanteperdrix]

GSM909@domain.hid wrote:
 > Hello
 > 
 > I have run a few programs with Xenomai tasks and have no problems. But I notice that the time between ISR and RT task ( RT task is suspended and resumed by the ISR) is shorter when Linux have a lot of work ( average load around 10 ) as when Linux has nothing to do( al : 0.05 ). 

Do you observe this for worst case, or for average case latencies? Do
you observe this when you boot with the idle=poll parameter ?

When idle, Linux uses the 'hlt' instruction, that stops the CPU until an
interrupt happen, maybe waking up from this state take a little bit more
time than when an interrupt is received directly?

-- 


					    Gilles Chanteperdrix.

Re: [Xenomai-help] Time between ISR and RT Task

[GSM909]

GSM909@domain.hid wrote:
 > Hello
 >
 > I have run a few programs with Xenomai tasks and have no problems. But I notice that the time between ISR and RT task ( RT task is suspended and resumed by the ISR) is shorter when Linux have a lot of work ( average load around 10 ) as when Linux has nothing to do( al : 0.05 ). 

Do you observe this for worst case, or for average case latencies? Do you observe this when you boot with the idle=poll parameter ?

When idle, Linux uses the 'hlt' instruction, that stops the CPU until an interrupt happen, maybe waking up from this state take a little bit more time than when an interrupt is received directly?

How can I set idel = poll ?
and what are other options for idel ? 

Regards 
Ted
-- 


					    Gilles Chanteperdrix.



-- 


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Re: [Xenomai-help] Time between ISR and RT Task

[Gilles Chanteperdrix]

GSM909@domain.hid wrote:
 > GSM909@domain.hid wrote:
 >  > Hello
 >  >
 >  > I have run a few programs with Xenomai tasks and have no problems. But I notice that the time between ISR and RT task ( RT task is suspended and resumed by the ISR) is shorter when Linux have a lot of work ( average load around 10 ) as when Linux has nothing to do( al : 0.05 ). 
 > 
 > Do you observe this for worst case, or for average case latencies? Do you observe this when you boot with the idle=poll parameter ?
 > 
 > When idle, Linux uses the 'hlt' instruction, that stops the CPU until an interrupt happen, maybe waking up from this state take a little bit more time than when an interrupt is received directly?
 > 
 > How can I set idel = poll ?

That's idle, not idel. The way to pass this option to the kernel depend
on the bootloader you are using. If using lilo on x86, add a line:

append="idle=poll"

to the /etc/lilo.conf section for the image you are booting (if there is
already an "append" line, then add "idle=poll" to this line)

If using grub on x86, add idle=poll to the /boot/grub/menu.lst line
beginning with "kernel" for the xenomai kernel.

Anyway, you should let the latency test run a few hours for a given
configuration before concluding anything, the worst case latency does
not show up so easily.

-- 


					    Gilles Chanteperdrix.

Re: [Xenomai-help] Time between ISR and RT Task

[newsletter]

Sorry

My System:
MPC8270 (PowerPC)
with uboot

Denx Linux und Xenomai Realtime Framework :)

thx for Helping


Gilles Chanteperdrix wrote:
> GSM909@domain.hid wrote:
>  > GSM909@domain.hid wrote:
>  >  > Hello
>  >  >
>  >  > I have run a few programs with Xenomai tasks and have no problems. But I notice that the time between ISR and RT task ( RT task is suspended and resumed by the ISR) is shorter when Linux have a lot of work ( average load around 10 ) as when Linux has nothing to do( al : 0.05 ). 
>  > 
>  > Do you observe this for worst case, or for average case latencies? Do you observe this when you boot with the idle=poll parameter ?
>  > 
>  > When idle, Linux uses the 'hlt' instruction, that stops the CPU until an interrupt happen, maybe waking up from this state take a little bit more time than when an interrupt is received directly?
>  > 
>  > How can I set idel = poll ?
>
> That's idle, not idel. The way to pass this option to the kernel depend
> on the bootloader you are using. If using lilo on x86, add a line:
>
> append="idle=poll"
>
> to the /etc/lilo.conf section for the image you are booting (if there is
> already an "append" line, then add "idle=poll" to this line)
>
> If using grub on x86, add idle=poll to the /boot/grub/menu.lst line
> beginning with "kernel" for the xenomai kernel.
>
> Anyway, you should let the latency test run a few hours for a given
> configuration before concluding anything, the worst case latency does
> not show up so easily.
>
>   

Re: [Xenomai-help] Time between ISR and RT Task

[Gilles Chanteperdrix]

newsletter wrote:
 > Sorry
 > 
 > My System:
 > MPC8270 (PowerPC)
 > with uboot
 > 
 > Denx Linux und Xenomai Realtime Framework :)
 > 
 > thx for Helping

See the "bootargs" environment variable at:
http://www.denx.de/wiki/view/DULG/UBootEnvVariables

The commands to set and save environment variables are explained here:
http://www.denx.de/wiki/view/DULG/UBootCmdGroupEnvironment

-- 


					    Gilles Chanteperdrix.