a few question on threads affinity and CPU shielding.

a few question on threads affinity and CPU shielding.

[Nicolas Castagné]

Hi all,

I  was very pleased that some patches for controlling CPU affinities  
were merged in the 2.5 (and 2.6) releases of the kernel.

Where may I find precisions on the patches that are now included ?

Especially, with the 2.6 release :
- is it possible to control the cpu affinity of threads (as for  
processes) ?
- is there also a patch to shield cpu against the scheduler ?
- is there also a patch to shield cpu against all interruptions  
(especially hard clock interrups) ?

We here are (very) used to SGI IRIX real time facilities, but also very  
new to linux.
We plan on porting our hard-real-time applications for multisensorial  
simulation on linux. These questions are very important to us.

Thx a lot in advance,
and please believe I am VERY sorry if this is not the correct list for  
my questions, and if I disturbed serious work ;-).
If so, please let me know !

Nicolas
------------------------------------------------------------------------ 
--------------------------
Dr Nicolas CASTAGNE
Researcher, IR de l'ACROE / ICA,

Association pour la Création et la Recherche
	sur les Outils d'Expression
Laboratoire Informatique et Création Artistique
INPG,
46 av. F. Viallet, 38000 Grenoble, France.

pro : (33) 4 76 57 46 60
fax : (33) 4 76 57 48 89
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Re: a few question on threads affinity and CPU shielding.

[Tim Hockin]

On Mon, Dec 01, 2003 at 06:43:16PM +0100, Nicolas Castagné wrote:
> I  was very pleased that some patches for controlling CPU affinities  
> were merged in the 2.5 (and 2.6) releases of the kernel.
> 
> Where may I find precisions on the patches that are now included ?

> - is there also a patch to shield cpu against the scheduler ?

I have a patch around that does this (against RedHat's backported O(1)).
Forward porting it should be no more difficult that creating it in the first
place :)  I was waiting until after 2.6.x was more stable to offer it.

> - is there also a patch to shield cpu against all interruptions  
> (especially hard clock interrups) ?

This could be added to my patch.

What my patch added was a sched_setprocstate() syscall, which lets you set a
CPU's run state.  Currently I support:

ENABLED - run any task
RESTRICTED - run only tasks with (cpus_allowed == 1 << cpu)
ISOLATED - run only tasks with
	(cpus_allowed == 1 << cpu && cpus_allowed_mask == 1 << cpu)

Tim

Re: a few question on threads affinity and CPU shielding.

[Dimitri Sivanich]

>We here are (very) used to SGI IRIX real time facilities

Nicolas,

You might be interested to know that there is an Altix real time project in
progress.  SGI is currently working on porting our real time facilities to
Linux with support beginning in the 2.6 kernel release (for Altix) timeframe.

Dimitri