[Intel-gfx] [PATCH 3/3] drm/i915: Use insert_page for pwrite_fast

[Chris Wilson]

On Thu, Nov 05, 2015 at 12:53:20PM +0000, Tvrtko Ursulin wrote:
> 
> On 05/11/15 12:42, Chris Wilson wrote:
> >On Thu, Nov 05, 2015 at 12:37:46PM +0000, Tvrtko Ursulin wrote:
> >>
> >>On 05/11/15 11:45, ankitprasad.r.sharma at intel.com wrote:
> >>>From: Ankitprasad Sharma <ankitprasad.r.sharma at intel.com>
> >>>
> >>>In pwrite_fast, map an object page by page if obj_ggtt_pin fails. First,
> >>>we try a nonblocking pin for the whole object (since that is fastest if
> >>>reused), then failing that we try to grab one page in the mappable
> >>>aperture. It also allows us to handle objects larger than the mappable
> >>>aperture (e.g. if we need to pwrite with vGPU restricting the aperture
> >>>to a measely 8MiB or something like that).
> >>
> >>Aperture in aperture, reminds me of those "Yo dawg I've heard you
> >>like X so I've put X in your X so you can Y while you Y" jokes. :D
> >>
> >>Would using the partial view code be interesting for this? Might be
> >>faster due to larger chunks possible, or slower due more expensive
> >>set up time, I don't know.
> >
> >It's the wrong abstraction.
> 
> Looks the same to me, only difference is the size.

There are many places that insert-page is used where we cannot do a
partial-pin.
 
> Why not just to the page aperture then for simplicity? If there is
> any performance gain from trying the full VMA first then why there
> wouldn't be some to try with the partial VMA?

obj->base.size >> PAGE_SHIFT x partial pages is not even funny.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre