Plan: BO move throttling for visible VRAM evictions

[Alex Deucher]

On Tue, Mar 28, 2017 at 4:29 AM, Christian König
<deathsimple at vodafone.de> wrote:
> Am 28.03.2017 um 08:00 schrieb Michel Dänzer:
>>
>> On 28/03/17 12:50 PM, zhoucm1 wrote:
>>>
>>> On 2017年03月28日 10:40, Michel Dänzer wrote:
>>>>
>>>> On 27/03/17 04:53 PM, Zhou, David(ChunMing) wrote:
>>>>>
>>>>> For APU special case, can we prevent eviction happening between VRAM
>>>>> <----> GTT?
>>>>
>>>> We can, if we can close the performance gap between VRAM and GTT. We
>>>> measured around 30% gap a while ago, though right now I'm only measuring
>>>> ~5%, but the test system has slower RAM now (still dual channel though).
>>>
>>> My impression VRAM and GTT have no much difference for APU case, if I'm
>>> wrong, pls correct me.
>>
>> The Mesa patch below makes radeonsi use mostly GTT instead of mostly
>> VRAM, and slows down Unigine Valley by about 5% on my desktop Kaveri.
>> You can try it for yourself.
>
>
> Additional to that you still need the stolen VRAM on APUs for page tables
> and DCE.

Actually DCE on CZ/BR/ST can use GTT as well, we just don't currently
allow it.  Older APUs did require "vram" however.

Alex

>
> So we need to keep the eviction from VRAM to GTT enabled, but what we don't
> do is swapping them back in because Marek added the GTT flags on APUs as
> extra domain to look into.
>
> In other word once BOs are removed from VRAM they are only swapped back in
> if the hardware needs it.
>
> Regards,
> Christian.
>
>>
>>
>> diff --git a/src/gallium/drivers/radeon/r600_buffer_common.c
>> b/src/gallium/drivers/radeon/r600_buffer_common.c
>> index da6f0206d7..47661cab76 100644
>> --- a/src/gallium/drivers/radeon/r600_buffer_common.c
>> +++ b/src/gallium/drivers/radeon/r600_buffer_common.c
>> @@ -175,9 +175,11 @@ void r600_init_resource_fields(struct
>> r600_common_screen *rscreen,
>>           * placements even with a low amount of stolen VRAM.
>>           */
>>          if (!rscreen->info.has_dedicated_vram &&
>> -           (rscreen->info.drm_major < 3 || rscreen->info.drm_minor < 6)
>> &&
>> -           res->domains == RADEON_DOMAIN_VRAM)
>> -               res->domains = RADEON_DOMAIN_VRAM_GTT;
>> +           res->domains == RADEON_DOMAIN_VRAM &&
>> +           !(res->b.b.bind & PIPE_BIND_SCANOUT)) {
>> +          res->domains = RADEON_DOMAIN_GTT;
>> +          res->flags |= RADEON_FLAG_GTT_WC;
>> +       }
>>
>>          if (rscreen->debug_flags & DBG_NO_WC)
>>                  res->flags &= ~RADEON_FLAG_GTT_WC;
>>
>>
>>
>
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