[Mesa-dev] [PATCH 2/2] RFC: radeon/compute: Limit allocations for VRAM-based chips to 3/4 VRAM

[Michel Dänzer]

On 10/06/17 12:43 AM, Aaron Watry wrote:
> On Wed, Jun 7, 2017 at 11:12 PM, Aaron Watry <awatry at gmail.com> wrote:
>> On Wed, Jun 7, 2017 at 9:15 PM, Michel Dänzer <michel at daenzer.net> wrote:
>>> On 08/06/17 03:42 AM, Marek Olšák wrote:
>>>> On Wed, Jun 7, 2017 at 4:10 PM, Aaron Watry <awatry at gmail.com> wrote:
>>>>> On Mon, Jun 5, 2017 at 3:07 PM, Marek Olšák <maraeo at gmail.com> wrote:
>>>>>>
>>>>>> Can you make the change in radeon_drm_winsys.c instead?
>>>>>
>>>>> Something like the following?
>>>>>
>>>>> diff --git a/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c
>>>>> b/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c
>>>>> index a485615ae4..44948f49ef 100644
>>>>> --- a/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c
>>>>> +++ b/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c
>>>>> @@ -365,6 +365,8 @@ static bool do_winsys_init(struct radeon_drm_winsys *ws)
>>>>>      /* Radeon allocates all buffers as contigous, which makes large allocations
>>>>>       * unlikely to succeed. */
>>>>>      ws->info.max_alloc_size = MAX2(ws->info.vram_size,
>>>>> ws->info.gart_size) * 0.7;
>>>>> +    if (ws->info.has_dedicated_vram)
>>>>> +        ws->info.max_alloc_size = MIN2(ws->info.vram_size * 0.7,
>>>>> ws->info.max_alloc_size);
>>>>>      if (ws->info.drm_minor < 40)
>>>>>          ws->info.max_alloc_size = MIN2(ws->info.max_alloc_size, 256*1024*1024);
>>>>
>>>> Yes, feel free to push that.
>>>
>>> That also affects PIPE_CAP_MAX_TEXTURE_BUFFER_SIZE, is that intended?
>>
>> Not necessarily.
>>
>> Part of the reason that I had originally put this in
>> r600_pipe_common.c under the compute params was that I didn't feel
>> comfortable changing this for all workload types. There's evidence
>> that implies that the closed-source AMD CL runtime limits global
>> allocations to either 256MB or 1/4 VRAM (on a 1GB card), so 70% of the
>> max of GART/VRAM seems a bit high for us to report. I'll probably
>> check around a bit and see what the prevailing limits seem to be and
>> if lowering the absolute max might make sense here (for compute loads
>> only), as a failure to allocate the requested amount of memory seems
>> to result in system hangs shortly thereafter, and I'd like to get the
>> frequency of those occurrences down a bit.
> 
> At least in Windows 10 using the AMD binary CL runtime, it reports
> global memory size of 2GB and max allocation of 1GB for the 1GB card
> that I've got.  Whether that's being calculated as max allocation =
> VRAM-size, or 50% of global memory size is an unknown. I'm not sure if
> you can easily adjust the gart size in windows. So my original theory
> of 1/4 VRAM seems to be limited to other cards or older drivers/OSes.
> 
> Given that Marek/Nicolai want to stick this in radeon_drm_winsys.c,
> I'm ok with putting it there.  I think it still makes sense to limit
> the max allocation to a percentage of VRAM when the card has its own
> memory available for the reasons already mentioned by Nicolai. Whether
> 70% is a good number is another question, but one thing at a time.
> 
> Any objections Michel, or were you just raising the point that it
> affected the texture allocation sizes just to make sure we were aware?

Right, just wanted to make sure everybody's aware.


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