Re: [PATCH net] xsk: remove cheap_dma optimization

[Daniel Borkmann]

On 6/28/20 7:16 PM, BjÃrn TÃpel wrote:
> On 2020-06-27 09:04, Christoph Hellwig wrote:
> > On Sat, Jun 27, 2020 at 01:00:19AM +0200, Daniel Borkmann wrote:
> > > Given there is roughly a ~5 weeks window at max where this removal could
> > > still be applied in the worst case, could we come up with a fix / proposal
> > > first that moves this into the DMA mapping core? If there is something that
> > > can be agreed upon by all parties, then we could avoid re-adding the 9%
> > > slowdown. :/
> >
> > I'd rather turn it upside down - this abuse of the internals blocks work
> > that has basically just missed the previous window and I'm not going
> > to wait weeks to sort out the API misuse. But we can add optimizations
> > back later if we find a sane way.
>
> I'm not super excited about the performance loss, but I do get
> Christoph's frustration about gutting the DMA API making it harder for
> DMA people to get work done. Lets try to solve this properly using
> proper DMA APIs.

Ok, fair enough, please work with DMA folks to get this properly integrated and
restored then. Applied, thanks!