[uClinux-dev] Excluding one of n Cores

Paul Chavent paul.chavent at fnac.net
Tue Jul 30 06:22:41 EDT 2013


On 07/29/2013 12:51 PM, Michael Schnell wrote:
> Hi Experts.

I'm not an expert. But i give you my ("standard" linux kernel) point of view (don't know if it works with uClinux).

>
> Is there a kind of "official" way to set aside one of the available cores in an SMP system from the Linux OS to do deeply embedded extremely-low-latency stuff in a kind of single task "main loop" type environment ? I.e. creating a true coprocessor from an SMP hardware.
>
> Some of the problems that come in ind here include:
>
>   - how to make the Linux initialization ignore one of the available cores  or free a core later on ?

See the isolcpu kernel parameter.

>   - how to have  a Linux task start the free running main loop ?
>   - how to assign certain interrupts to that core and have ISRs run there only dedicatedly interrupting the "main loop" and not ever being blocked by any Linux activity ?

Something like interrupt balancing ?
http://subversion.ffado.org/wiki/IrqPriorities

I got this link from the https://rt.wiki.kernel.org/index.php/RT:Tips page.

>   - what about MMU issues ?

I never tried to enable mmu with uclinux. But on a "standard" linux i use mlock to deal with mmu, caches etc.

>
> For example I (e.g.) would like a (now rather cheap) standard quadcore ARM Cortex A9 processor chip and modify a Debian distribution in a way that support this stuff.
>
> Thanks,
> -Michael
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