[Xenomai] Unexpected CPU assignment on iMX6Q

[Xenomai] Unexpected CPU assignment on iMX6Q

[Javier Martínez Cantos]

Hi everybody,

I'm currently working on Toradex Apalis iMX6Q (4 cores) with Xenomai 
2.6.4. The system runs fine.

However, I'm playing around with rt_task_create and T_CPU obtaining the 
following results:

- T_CPU(0-3) leads to task creation on expected core, i.e. 1 to 4,

- while T_CPU(>3) leads to task creation always on first core.

Affinity is configured as follows:

cat /proc/xenomai/affinity
0000000f

I expect rt_task_create to return an EINVAL error or something like that 
when T_CPU is higher than RTHAL_NR_CPUS - 1.

Could RTHAL_NR_CPUS has a value higher than 4? How can I check this? I 
have already checked that CONFIG_NR_CPUS is 4.

On runtime, how can I query the "task to core assignment" through 
Xenomai API?

Thanks in advance.

-- 


Javier Martínez Cantos

Sistemas embarcados



	

Julián Camarillo, 21 B, 3ª Planta 28037 Madrid, España

	

(+34) 91 440 18 33

	

jmartinez@ixion.es

	

http://www.ixion.es <http://www.ixion.es/>

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-- 


Javier Martínez Cantos

Sistemas embarcados



	

Julián Camarillo, 21 B, 3ª Planta 28037 Madrid, España

	

(+34) 91 440 18 33

	

jmartinez@ixion.es 
<.////172.20.31.5/datos/IXION/Info_public/Logos/Nueva%2520imagen%2520corporativa/Plantillas/xxxx@ixion.es%2520>

	

http://www.ixion.es <http://www.ixion.es/>

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Re: [Xenomai] Unexpected CPU assignment on iMX6Q

[Gilles Chanteperdrix]

On Mon, Feb 15, 2016 at 12:39:29PM +0100, Javier Martínez Cantos wrote:
> Hi everybody,
> 
> I'm currently working on Toradex Apalis iMX6Q (4 cores) with Xenomai 
> 2.6.4. The system runs fine.
> 
> However, I'm playing around with rt_task_create and T_CPU obtaining the 
> following results:
> 
> - T_CPU(0-3) leads to task creation on expected core, i.e. 1 to 4,
> 
> - while T_CPU(>3) leads to task creation always on first core.
> 
> Affinity is configured as follows:
> 
> cat /proc/xenomai/affinity
> 0000000f
> 
> I expect rt_task_create to return an EINVAL error or something like that 
> when T_CPU is higher than RTHAL_NR_CPUS - 1.

The affinity is used when starting the task with rt_task_start, not
when creating it. And indeed, rt_task_start should return -EINVAL if
no cpu is found for running the task.

> 
> Could RTHAL_NR_CPUS has a value higher than 4? How can I check this? I 
> have already checked that CONFIG_NR_CPUS is 4.

NR_CPUS does not matter, xnpod_start_thread does a "bitwise and" with
cpu_online_mask.

> 
> On runtime, how can I query the "task to core assignment" through 
> Xenomai API?

I am not sure there is a way. You can check /proc/xenomai/sched or
/proc/xenomai/stat though.

-- 
					    Gilles.
https://click-hack.org

Re: [Xenomai] Unexpected CPU assignment on iMX6Q

[Javier Martínez Cantos]

On 15/02/16 13:15, Gilles Chanteperdrix wrote:
> On Mon, Feb 15, 2016 at 12:39:29PM +0100, Javier Martínez Cantos wrote:
>> Hi everybody,
>>
>> I'm currently working on Toradex Apalis iMX6Q (4 cores) with Xenomai
>> 2.6.4. The system runs fine.
>>
>> However, I'm playing around with rt_task_create and T_CPU obtaining the
>> following results:
>>
>> - T_CPU(0-3) leads to task creation on expected core, i.e. 1 to 4,
>>
>> - while T_CPU(>3) leads to task creation always on first core.
>>
>> Affinity is configured as follows:
>>
>> cat /proc/xenomai/affinity
>> 0000000f
>>
>> I expect rt_task_create to return an EINVAL error or something like that
>> when T_CPU is higher than RTHAL_NR_CPUS - 1.
> The affinity is used when starting the task with rt_task_start, not
> when creating it. And indeed, rt_task_start should return -EINVAL if
> no cpu is found for running the task.
Ok, I misunderstood. Anyway it is unexpected.

Once rt_task_create is called with -say- T_CPU(20), rt_task_start 
returns 0 (success) and the target task is launched on first core (index 0).

What's wrong?
>> Could RTHAL_NR_CPUS has a value higher than 4? How can I check this? I
>> have already checked that CONFIG_NR_CPUS is 4.
> NR_CPUS does not matter, xnpod_start_thread does a "bitwise and" with
> cpu_online_mask.
I'll explore this path.
>> On runtime, how can I query the "task to core assignment" through
>> Xenomai API?
> I am not sure there is a way. You can check /proc/xenomai/sched or
> /proc/xenomai/stat though.
>
Thank you Gilles.

-- 


Javier Martínez Cantos

Sistemas embarcados



	

Julián Camarillo, 21 B, 3ª Planta 28037 Madrid, España

	

(+34) 91 440 18 33

	

jmartinez@ixion.es 
<.////172.20.31.5/datos/IXION/Info_public/Logos/Nueva%2520imagen%2520corporativa/Plantillas/xxxx@ixion.es%2520>

	

http://www.ixion.es <http://www.ixion.es/>

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