[PATCH 3/3] drm/amdgpu: add gtt_sys_limit

[Michel Dänzer]

On 27/06/17 08:39 AM, John Brooks wrote:
> On Mon, Jun 26, 2017 at 03:39:57PM +0200, Christian König wrote:
>> From: Christian König <christian.koenig at amd.com>
>>
>> Limit the size of the GART table for the system domain.
>>
>> This saves us a bunch of visible VRAM, but also limitates the maximum BO size we can swap out.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
> 
> Hmm.
> 
> On my system, GTT is 4096MiB (1048576 pages). For this, the table takes up
> 1048576*8 bytes = 8MiB. Reducing GTT to 256MiB (65536 pages) would reduce the
> size of the table to 512 KiB. A relatively large saving, to be sure. But in the
> grander scheme of things, is saving 7.5MiB (3% of visible VRAM @ 256M) worth
> cutting GTT memory by a factor of 16?

I'm afraid not, especially since it would limit the maximum BO size to <
256MB, if I understand correctly. Pretty sure that would cause failures
with real world apps.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer