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

[Chris Wilson]

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.
 
> And the use above was to a mmaped area, which I think should be
> considered to behave like CPU paged memory? Otherwise kind of defeats
> mmap purpose.

I was making the observation just in case someone wanted to go through
the whole code base fixing up the hardcoded 4096 constants.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre