[PATCH libdrm] amdgpu: add a faster BO list API

[Christian König]

Am 09.01.19 um 17:14 schrieb Marek Olšák:
> On Wed, Jan 9, 2019 at 8:09 AM Christian König 
> <ckoenig.leichtzumerken at gmail.com 
> <mailto:ckoenig.leichtzumerken at gmail.com>> wrote:
>
>     Am 09.01.19 um 13:36 schrieb Marek Olšák:
>>
>>
>>     On Wed, Jan 9, 2019, 5:28 AM Christian König
>>     <ckoenig.leichtzumerken at gmail.com
>>     <mailto:ckoenig.leichtzumerken at gmail.com> wrote:
>>
>>         Looks good, but I'm wondering what's the actual improvement?
>>
>>
>>     No malloc calls and 1 less for loop copying the bo list.
>
>     Yeah, but didn't we want to get completely rid of the bo list?
>
>
> If we have multiple IBs (e.g. gfx + compute) that share a BO list, I 
> think it's faster to send the BO list to the kernel only once.

That's not really faster.

The only thing we safe us is a single loop over all BOs to lockup the 
handle into a pointer and that is only a tiny fraction of the overhead.

The majority of the overhead is locking the BOs and reserving space for 
the submission.

What could really help here is to submit gfx+comput together in just one 
CS IOCTL. This way we would need the locking and space reservation only 
once.

It's a bit of work in the kernel side, but certainly doable.

Christian.

>
> Marek
>
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