[Mesa-dev] [PATCH 1/2] gallium: Add PIPE_CAP_USER_MEMORY_PAGE_SIZE for page size of user pointers

[Jan Vesely]

On Wed, 2017-08-16 at 23:49 -0400, Alex Deucher wrote:
> On Wed, Aug 16, 2017 at 11:34 PM, Michel Dänzer <michel at daenzer.net> wrote:
> > On 17/08/17 12:33 PM, Aaron Watry wrote:
> > > On Wed, Aug 16, 2017 at 9:48 PM, Alex Deucher <alexdeucher at gmail.com> wrote:
> > > > On Wed, Aug 16, 2017 at 10:39 PM, Michel Dänzer <michel at daenzer.net> wrote:
> > > > > On 17/08/17 10:52 AM, Aaron Watry wrote:
> > > > > > PIPE_CAP_RESOURCE_FROM_USER_MEMORY says that size must be page aligned,
> > > > > > but doesn't necessarily say anything about the size of those pages.
> > > > > 
> > > > > Is there any case known so far where it's not the CPU page size?
> > > > 
> > > > It's always the CPU page size.  The limitation is not a hw limitation,
> > > > it's a sw limitation with the way the kernel handles creating BOs from
> > > > user memory.
> > > 
> > > So this won't change with the 2MB pages that are coming up for Vega?
> > 
> > I don't think it will, that's only about VRAM.
> 
> It applies to system memory as well, e.g., transparent huge pages, or
> larger page sizes in general.  I don't think that affects this
> however.

what's so special about Vega 2MB pages? I thought GPUVM fragments could
specify any size (power of 2 > 4KB) even if TLBs supports anly select
few.
I remember using 4KB, 2MB, and 1GB pages with nice performance benefits
on Kaveri (using ATS, ROCm setup).

Jan

> 
> Alex
> 
> > 
> > 
> > > If so, I guess I can just use getpagesize() in patch 2 for now and skip the CAP.
> > 
> > Right.
> > 
> > 
> > --
> > Earthling Michel Dänzer               |               http://www.amd.com
> > Libre software enthusiast             |             Mesa and X developer
> 
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-- 
Jan Vesely <jan.vesely at rutgers.edu>
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