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SubjectRe: io resources and cached mappings (was: [git pull] drm patches for 2.6.27-rc1)

* Keith Packard <keithp@keithp.com> wrote:

> On Mon, 2008-10-20 at 13:58 +0200, Ingo Molnar wrote:
>
> > yes but note that by caching the whole mapping on 64-bit we get
> > everything we want: trivially lockless, works from any CPU, can be
> > preempted at will, and there are no ugly INVLPG flushes anywhere.
>
> I was assuming that on 64-bit, the map would be created at driver init
> time and be left in place until the driver closed; if that's what you
> mean by 'caching', then yes, we should cache the map.

correct.

> > 32-bit we should handle as well but not design for it.
>
> As long as we get kmap_atomic-like performance, and we get to simplify
> our code, I'm up for it.

okay. So ... mind sending your io_mapping patch as a generic facility?
It looks all good to me in its present form, except that it should live
in include/linux/io.h, not in the drivers/gpu/drm/i915/io_reserve.h file
:-)

also, please send at least two patches, so that we can look at (and
possibly merge) the generic facility in isolation.

Ingo


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