[Lsf-pc] [LSF/MM/BPF proposal]: Physr discussion

[Matthew Wilcox]

On Mon, Jan 23, 2023 at 11:36:51AM -0800, Dan Williams wrote:
> Jason Gunthorpe via Lsf-pc wrote:
> > I would like to have a session at LSF to talk about Matthew's
> > physr discussion starter:
> > 
> >  https://lore.kernel.org/linux-mm/YdyKWeU0HTv8m7wD@casper.infradead.org/
> > 
> > I have become interested in this with some immediacy because of
> > IOMMUFD and this other discussion with Christoph:
> > 
> >  https://lore.kernel.org/kvm/4-v2-472615b3877e+28f7-vfio_dma_buf_jgg@nvidia.com/
> 
> I think this is a worthwhile discussion. My main hangup with 'struct
> page' elimination in general is that if anything needs to be allocated

You're the first one to bring up struct page elimination.  Neither Jason
nor I have that as our motivation.  But there are reasons why struct page
is a bad data structure, and Xen proves that you don't need to have such
a data structure in order to do I/O.

> When I read "general interest across all the driver subsystems" it is
> hard not to ask "have all possible avenues to enable 'struct page' been
> exhausted?"

Yes, we should definitely expend yet more resources chasing a poor
implementation.