Re: kmap_atomic_pfn for PCI BAR access?

[Arjan van de Ven]

On Thu, 26 Jun 2008 03:36:14 -0700
Arjan van de Ven <arjan@xxxxxxxxxxxxx> wrote:

> On Thu, 26 Jun 2008 07:02:15 +0100 (IST)
> Dave Airlie <airlied@xxxxxxxx> wrote:
> 
> > > >   
> > > 
> > > Anything that does any kind of pagetable manipulation needs to do
> > > tlb flushes. kunmap_atomic handles the flushing.
> > 
> > It doesn't however need to do an IPI dance which is the worst part
> > of doing a tlb flush on SMP machines.
> > 
> > flushing local CPU tlbs is bad, but doing IPIs and waiting for
> > everyone else is brutal.
> 
> but you only do IPI's for the multithreaded case to cpus where you're
> running; otoh I guess games are multithreaded nowadays
eh never mind this is total bogus
yes a full ipi is needed.

note that with ioremap you may need certain tricks as well to deal with
cache type aliasing, depending on the type of ioremap you want (wc?)

> 
> > 
> > Dave.
> 
> 


-- 
If you want to reach me at my work email, use arjan@xxxxxxxxxxxxxxx
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/