Re: [PATCH][resubmit] x86: enable preemption in delay

[Pavel Machek <pavel@suse.cz>]

On Wed 2008-06-18 09:55:18, Ingo Molnar wrote:
> 
> * Marin Mitov <mitov@issp.bas.bg> wrote:
> 
> > Why not something like that (do keep in mind I am not an expert :-):
> > 
> > static void delay_tsc(unsigned long loops)
> > {
> > 	get and store the mask of allowed cpus;
> > 	/*     prevent the migration   */
> > 	set the mask of allowed cpus to the current cpu only;
> > 	/*     is it possible? could it be guaranteed?    */
> > 	loop for the delay;
> > 	restore the old mask of allowed cpus;
> > }
> > 
> > You have got the idea. Could it be realized? Is it more expensive than 
> > the current realization? So, comments, please.
> 
> hm, changing/saving/restorig cpus_allowed is really considered a 'heavy' 
> operation compared to preempt_disable(). On a 4096 CPUs box cpus_allowed 
> is 4096 bits which is half a kilobyte ...

Time to RLE the bitmap? 

<runs>							Pavel

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