[Intel-gfx] [PATCH i-g-t] tests/gem_mmap_gtt: Use PAGE_SIZE instead of hard coded value

[Daniel Vetter]

On Thu, Apr 30, 2015 at 12:22:56PM +0100, Chris Wilson wrote:
> On Thu, Apr 30, 2015 at 01:28:46PM +0300, Joonas Lahtinen wrote:
> > On ma, 2015-04-27 at 20:43 +0100, Chris Wilson wrote:
> > > On Mon, Apr 27, 2015 at 06:35:54PM +0100, Thomas Wood wrote:
> > > > On 24 April 2015 at 08:38, Joonas Lahtinen
> > > > <joonas.lahtinen at linux.intel.com> wrote:
> > > > > Now that there is PAGE_SIZE define, use it.
> > > > 
> > > > Thanks, I've pushed this patch. I also noticed PAGE_SIZE gets defined
> > > > in several tests, so at some point it might be worth moving it into
> > > > the library.
> > > 
> > > Be wary of these though. PAGE_SIZE should only ever be used wrt to struct
> > > page and not GPU pages. If you must, please use GTT_PAGE_SIZE instead.
> > 
> > Do we have a platform/case where these are different? Just asking out of
> > curiosity :)
> 
> Yes. We just haven't enabled big pages yet. The thought of getting globs
> of 64k contiguous physical memory isn't too appealing, but like with
> hugepages there are likely enough tasks that benefit.

I thought the verdict thus far was that hw engineers overspecced tlbs and
64k pages aren't really worth it except in some corner-case video code
workloads. Might have changed with the gen8+ pagetables, but I haven't
seen any new noises about this.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch