Re: [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache()

[Arjan van de Ven]

On Sun, 1 Mar 2009 02:48:22 +0100
Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:

> > the entire point of using movntq and friends was to save half the
> 
> I thought the point was to not pollute caches? At least that is 
> what I remember being told when I merged the patch.
> 

the reason that movntq and co are faster is because you avoid the
write-allocate behavior of the caches....

the cache polluting part of it I find hard to buy for general use (as
this discussion shows)... that will be extremely hard to measure as
a real huge thing, while the WA part is like a 1.5x to 2x thing.


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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/