[Xenomai-help] Known-to-work motherboards?

[Xenomai-help] Known-to-work motherboards?

[Stuart O Anderson]

Hello -

Is there a list of recent motherboards that are known to play nicely
with Xenomai?  I've run into problems with some machines (USB host
drops out, SATA doesn't work, etc) we have in the lab.  I've been able
to work around these problems in most cases.  However, since we're
buying a few new machines, I'd like to be able to order hardware that
I'm reasonably confident will work out-of-the-box with Xenomai.

If there isn't a list online that I've missed, is anyone running
xenomai on a relatively recent machine with 8 or more cores without
problems?  If so, can you provide hardware specs?

Thanks very much,

Stuart

Re: [Xenomai-help] Known-to-work motherboards?

[Gilles Chanteperdrix]

Stuart O Anderson wrote:
> Hello -
> 
> Is there a list of recent motherboards that are known to play nicely
> with Xenomai?  I've run into problems with some machines (USB host
> drops out, SATA doesn't work, etc) we have in the lab.  I've been able
> to work around these problems in most cases.

As answered to the questions you initially asked on this list, the only
known needed workaround is to disable MSI interrupts (I do not even know
if it is still needed). So, if you have other problems, we would be glad
to know it, because we like to think that when a kernel configuration
works with Linux, it works when enabling Xenomai. So, any motherboard
which works with Linux is supposed to work with Xenomai.

> If there isn't a list online that I've missed, is anyone running
> xenomai on a relatively recent machine with 8 or more cores without
> problems?  If so, can you provide hardware specs?

Xenomai will have scalability problems when running on an 8 cores system
(if you intend to run real-time tasks on each of the 8 cores).

-- 
					    Gilles.

Re: [Xenomai-help] Known-to-work motherboards?

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 908 bytes --]

Gilles Chanteperdrix wrote:
> Stuart O Anderson wrote:
>> If there isn't a list online that I've missed, is anyone running
>> xenomai on a relatively recent machine with 8 or more cores without
>> problems?  If so, can you provide hardware specs?
> 
> Xenomai will have scalability problems when running on an 8 cores system
> (if you intend to run real-time tasks on each of the 8 cores).
> 

We are running Xenomai on up to 4x4 boxes, but only with 1 or 2 cores
used by RT tasks. I've some patch hanging around that restricts Xenomai
(specifically its host timer hook) to a CPU subset in order to mitigate
the scalability issues - guess I should finally get it in shape and post it.

However, my point is: Massive parallel RT is not (yet) feasible with
Xenomai, but it is no black magic to have massive parallel non-RT load
living together with confined RT load on the same box.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 257 bytes --]

Re: [Xenomai-help] Known-to-work motherboards?

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Stuart O Anderson wrote:
>>> If there isn't a list online that I've missed, is anyone running
>>> xenomai on a relatively recent machine with 8 or more cores without
>>> problems?  If so, can you provide hardware specs?
>> Xenomai will have scalability problems when running on an 8 cores system
>> (if you intend to run real-time tasks on each of the 8 cores).
>>
> 
> We are running Xenomai on up to 4x4 boxes, but only with 1 or 2 cores
> used by RT tasks. I've some patch hanging around that restricts Xenomai
> (specifically its host timer hook) to a CPU subset in order to mitigate
> the scalability issues - guess I should finally get it in shape and post it.

The host timer already runs on only one CPU.

-- 
					    Gilles.

Re: [Xenomai-help] Known-to-work motherboards?

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 847 bytes --]

Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>> Stuart O Anderson wrote:
>>>> If there isn't a list online that I've missed, is anyone running
>>>> xenomai on a relatively recent machine with 8 or more cores without
>>>> problems?  If so, can you provide hardware specs?
>>> Xenomai will have scalability problems when running on an 8 cores system
>>> (if you intend to run real-time tasks on each of the 8 cores).
>>>
>> We are running Xenomai on up to 4x4 boxes, but only with 1 or 2 cores
>> used by RT tasks. I've some patch hanging around that restricts Xenomai
>> (specifically its host timer hook) to a CPU subset in order to mitigate
>> the scalability issues - guess I should finally get it in shape and post it.
> 
> The host timer already runs on only one CPU.

Not on x86.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 257 bytes --]

Re: [Xenomai-help] Known-to-work motherboards?

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Gilles Chanteperdrix wrote:
>>>> Stuart O Anderson wrote:
>>>>> If there isn't a list online that I've missed, is anyone running
>>>>> xenomai on a relatively recent machine with 8 or more cores without
>>>>> problems?  If so, can you provide hardware specs?
>>>> Xenomai will have scalability problems when running on an 8 cores system
>>>> (if you intend to run real-time tasks on each of the 8 cores).
>>>>
>>> We are running Xenomai on up to 4x4 boxes, but only with 1 or 2 cores
>>> used by RT tasks. I've some patch hanging around that restricts Xenomai
>>> (specifically its host timer hook) to a CPU subset in order to mitigate
>>> the scalability issues - guess I should finally get it in shape and post it.
>> The host timer already runs on only one CPU.
> 
> Not on x86.

Some time ago, when using the APIC (which was always the case on x86
SMP), the host timer was not even started, and the Linux APIC irqs were
triggered by a custom 8254 irq handler. Well, it seems things have
changed since then...

-- 
					    Gilles.

Re: [Xenomai-help] Known-to-work motherboards?

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 1474 bytes --]

Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>> Jan Kiszka wrote:
>>>> Gilles Chanteperdrix wrote:
>>>>> Stuart O Anderson wrote:
>>>>>> If there isn't a list online that I've missed, is anyone running
>>>>>> xenomai on a relatively recent machine with 8 or more cores without
>>>>>> problems?  If so, can you provide hardware specs?
>>>>> Xenomai will have scalability problems when running on an 8 cores system
>>>>> (if you intend to run real-time tasks on each of the 8 cores).
>>>>>
>>>> We are running Xenomai on up to 4x4 boxes, but only with 1 or 2 cores
>>>> used by RT tasks. I've some patch hanging around that restricts Xenomai
>>>> (specifically its host timer hook) to a CPU subset in order to mitigate
>>>> the scalability issues - guess I should finally get it in shape and post it.
>>> The host timer already runs on only one CPU.
>> Not on x86.
> 
> Some time ago, when using the APIC (which was always the case on x86
> SMP), the host timer was not even started, and the Linux APIC irqs were
> triggered by a custom 8254 irq handler. Well, it seems things have
> changed since then...

...around the Linux clocksource/clockevent rework. And it also makes
more sense with the number of cores increasing and NUMA becoming
standard. CPU-local timers are simply more efficient. That's why the
nklock hurts that any host tick must pass even if the core is not used
by Xenomai otherwise.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 257 bytes --]