Re: [PATCH v5 4/4] drm/amdgpu: track bo memory stats at runtime

[Tvrtko Ursulin <tvrtko.ursulin@igalia.com>]

On 22/10/2024 18:06, Christian König wrote:
> Am 22.10.24 um 18:46 schrieb Li, Yunxiang (Teddy):
>> [Public]
>>
>> I suppose we could add a field like amd-memory-private: to cover the 
>> private placements.
> 
> No, that is not really appropriate either. GWS, GDS and OA are not 
> memory in the first place.
> 
> Those BOs are HW blocks which the driver allocated to use.
> 
> So accounting them for the memory usage doesn't make any sense at all.
> 
> We could print them in the fdinfo as something special for statistics, 
> but it's probably not that useful.
> 
>>   When would a BO not have a placement, is it when it is being moved?
> 
> There are BOs which are only temporary, so when they are evicted their 
> backing store is just discarded.
> 
> Additional to that allocation of backing store is sometimes delayed 
> until the first use.

Would this work correctly if instead of preferred allowed mask was used?

Point being, to correctly support fdinfo stats drm-total-, *if* a BO 
*can* have a backing store at any point it should always be counted there.

*If* it currently has a placement it is drm-resident-.

If it has a placement but can be discarded it is drm-purgeable-. Etc.

Regards,

Tvrtko

> 
>>   Since we are tracking the state changes, I wonder if such situations 
>> can be avoided now so whenever we call these stat update functions the 
>> BO would always have a placement.
> 
> No, as I said before those use cases are perfectly valid. BO don't need 
> a backing store nor do they need a placement.
> 
> So the code has to gracefully handle that.
> 
> Regards,
> Christian.
> 
>>
>> Teddy
>