Re: [PATCH v5 0/9] mmu notifier provide context informations

[Jerome Glisse <jglisse@redhat.com>]

On Tue, Feb 19, 2019 at 01:19:09PM -0800, Dan Williams wrote:
> On Tue, Feb 19, 2019 at 12:58 PM Jerome Glisse <jglisse@redhat.com> wrote:
> >
> > On Tue, Feb 19, 2019 at 12:40:37PM -0800, Dan Williams wrote:
> > > On Tue, Feb 19, 2019 at 12:30 PM Jerome Glisse <jglisse@redhat.com> wrote:
> > > >
> > > > On Tue, Feb 19, 2019 at 12:15:55PM -0800, Dan Williams wrote:
> > > > > On Tue, Feb 19, 2019 at 12:04 PM <jglisse@redhat.com> wrote:
> > > > > >
> > > > > > From: Jérôme Glisse <jglisse@redhat.com>
> > > > > >
> > > > > > Since last version [4] i added the extra bits needed for the change_pte
> > > > > > optimization (which is a KSM thing). Here i am not posting users of
> > > > > > this, they will be posted to the appropriate sub-systems (KVM, GPU,
> > > > > > RDMA, ...) once this serie get upstream. If you want to look at users
> > > > > > of this see [5] [6]. If this gets in 5.1 then i will be submitting
> > > > > > those users for 5.2 (including KVM if KVM folks feel comfortable with
> > > > > > it).
> > > > >
> > > > > The users look small and straightforward. Why not await acks and
> > > > > reviewed-by's for the users like a typical upstream submission and
> > > > > merge them together? Is all of the functionality of this
> > > > > infrastructure consumed by the proposed users? Last time I checked it
> > > > > was only a subset.
> > > >
> > > > Yes pretty much all is use, the unuse case is SOFT_DIRTY and CLEAR
> > > > vs UNMAP. Both of which i intend to use. The RDMA folks already ack
> > > > the patches IIRC, so did radeon and amdgpu. I believe the i915 folks
> > > > were ok with it too. I do not want to merge things through Andrew
> > > > for all of this we discussed that in the past, merge mm bits through
> > > > Andrew in one release and bits that use things in the next release.
> > >
> > > Ok, I was trying to find the links to the acks on the mailing list,
> > > those references would address my concerns. I see no reason to rush
> > > SOFT_DIRTY and CLEAR ahead of the upstream user.
> >
> > I intend to post user for those in next couple weeks for 5.2 HMM bits.
> > So user for this (CLEAR/UNMAP/SOFTDIRTY) will definitly materialize in
> > time for 5.2.
> >
> > ACKS AMD/RADEON https://lkml.org/lkml/2019/2/1/395
> > ACKS RDMA https://lkml.org/lkml/2018/12/6/1473
> 
> Nice, thanks!
> 
> > For KVM Andrea Arcangeli seems to like the whole idea to restore the
> > change_pte optimization but i have not got ACK from Radim or Paolo,
> > however given the small performance improvement figure i get with it
> > i do not see while they would not ACK.
> 
> Sure, but no need to push ahead without that confirmation, right? At
> least for the piece that KVM cares about, maybe that's already covered
> in the infrastructure RDMA and RADEON are using?

The change_pte() for KVM is just one bit flag on top of the rest. So
i don't see much value in saving this last patch. I will be working
with KVM folks to merge KVM bits in 5.2. If they do not want that then
removing that extra flags is not much work.

But if you prefer than Andrew can drop the last patch in the serie.

Cheers,
Jérôme