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

["Marek Olšák" <maraeo-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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On Wed, Jan 9, 2019 at 1:41 PM Christian König <
ckoenig.leichtzumerken-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Am 09.01.19 um 17:14 schrieb Marek Olšák:
>
> On Wed, Jan 9, 2019 at 8:09 AM Christian König <
> ckoenig.leichtzumerken-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>> Am 09.01.19 um 13:36 schrieb Marek Olšák:
>>
>>
>>
>> On Wed, Jan 9, 2019, 5:28 AM Christian König <
>> ckoenig.leichtzumerken-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org 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.
>

OK. Any objections to this patch?

Thanks,
Marek

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