Re: [PATCH hmm 15/15] mm/hmm: remove hmm_mirror and related

[Jerome Glisse <jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Mon, Oct 21, 2019 at 06:57:42PM +0000, Jason Gunthorpe wrote:
> On Mon, Oct 21, 2019 at 02:38:24PM -0400, Jerome Glisse wrote:
> > On Tue, Oct 15, 2019 at 03:12:42PM -0300, Jason Gunthorpe wrote:
> > > From: Jason Gunthorpe <jgg@mellanox.com>
> > > 
> > > The only two users of this are now converted to use mmu_range_notifier,
> > > delete all the code and update hmm.rst.
> > 
> > I guess i should point out that the reasons for hmm_mirror and hmm
> > was for:
> >     1) Maybe define a common API for userspace to provide memory
> >        placement hints (NUMA for GPU)
> 
> Do you think this needs special code in the notifiers?

Just need a place where to hang userspace policy hint the hmm_range
was the prime suspect. I need to revisit this once the nouveau user
space is in better shape.

> 
> >     2) multi-devices sharing same mirror page table
> 
> Oh neat, but I think this just means the GPU driver has to register a
> single notifier for multiple GPUs??

Yes that was the idea a single notifier with share page table, but
at this time this is non existent code so no need to hinder change
just for the sake of it.

> 
> > But support for multi-GPU in nouveau is way behind and i guess such
> > optimization will have to re-materialize what is necessary once that
> > happens.
> 
> Sure, it will be easier to understand what is needed with a bit of
> code!
> 
> > Note this patch should also update kernel/fork.c and the mm_struct
> > definition AFAICT. With those changes you can add my:
> 
> Can you please elaborate what updates you mean? I'm not sure. 
> 
> Maybe I already got the things you are thinking of with the get/put
> changes?

Oh i forgot this was already taken care of by this. So yes all is
fine:

Reviewed-by: Jérôme Glisse <jglisse@redhat.com>

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