Plan: BO move throttling for visible VRAM evictions

[Christian König]

Am 28.03.2017 um 15:58 schrieb 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.

I'm not so deep into that, but as far as I understand it at least one 
DCE fetch unit needs to be contiguous.

So you need 64K pages (or at minimum 8/16K pages) for your GTT 
implementation to support that if I understood it correctly.

Christian.

>
> 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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