On 09/14/2011 05:00 PM, Jeff Weber wrote:
> On Wed, Sep 14, 2011 at 8:13 AM, Gilles Chanteperdrix <
> [email protected]> wrote:
>
>> On 09/14/2011 02:18 PM, Henri Roosen wrote:
>> [snip]
>>>
>>> What I would like to do is to run the Xenomai realtime threads on one
>>> core of the multi-core CPU. And I would like to reserve this core only
>>> for the Xenomai realtime threads.
>>>
>> [snip]
>> The kernel has an "isolcpus" option, which allows to specify which cpus
>> should not be used by Linux.
>>
>> See Documentation/kernel-parameters.txt in the linux kernel sources for
>> an explanation.
>>
>>
> I tried to do this a year ago with the kernel isolcpus option, but could not
> get this to work:
>
>> Gilles Chanteperdrix to Jeff, xenomai-help
>> Jeff wrote:
>>> What is the best method for segregating Xenomai and Linux by CPU? I was
>>> unable to do this cleanly using /proc/xenomai/affinity for Xenomai,
>>> together with the Linux isolcpus boot option. Details below.
>>
>> I have no definite answer, I have not checked. What I suspect, however,
>> is that when you try and force an affinity for a Xenomai thread, it
>> tries and apply this affinity in secondary mode, i.e. as a plain Linux
>> thread. So, will fail if the target thread is not in the "isolcpus"
>> mask. In other words, a Xenomai thread can not run on a CPU where Linux
>> threads can not run.
This explanation sounds like crap: looking at the documentation, it
seems that when using the "isolcpus" option, threads can run on an
isolated cpu if they force their affinity.
--
Gilles.
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