[RFC 00/11] THP support for zone device pages

[Francois Dugast]

On Sun, Jul 06, 2025 at 11:25:32AM +1000, Balbir Singh wrote:
> On 7/5/25 02:17, Zi Yan wrote:
> > On 4 Jul 2025, at 9:52, Francois Dugast wrote:
> > 
> >> Hi,
> >>
> >> On Fri, Mar 07, 2025 at 10:20:30AM +1100, Balbir Singh wrote:
> >>> On 3/7/25 10:08, Matthew Brost wrote:
> >>>> On Thu, Mar 06, 2025 at 03:42:28PM +1100, Balbir Singh wrote:
> >>>>
> >>>> This is an exciting series to see. As of today, we have just merged this
> >>>> series into the DRM subsystem / Xe [2], which adds very basic SVM
> >>>> support. One of the performance bottlenecks we quickly identified was
> >>>> the lack of THP for device pages—I believe our profiling showed that 96%
> >>>> of the time spent on 2M page GPU faults was within the migrate_vma_*
> >>>> functions. Presumably, this will help significantly.
> >>>>
> >>>> We will likely attempt to pull this code into GPU SVM / Xe fairly soon.
> >>>> I believe we will encounter a conflict since [2] includes these patches
> >>>> [3] [4], but we should be able to resolve that. These patches might make
> >>>> it into the 6.15 PR — TBD but I can get back to you on that.
> >>>>
> >>>> I have one question—does this series contain all the required core MM
> >>>> changes for us to give it a try? That is, do I need to include any other
> >>>> code from the list to test this out?
> >>>>
> >>>
> >>> Thank you, the patches are built on top of mm-everything-2025-03-04-05-51, which
> >>> includes changes by Alistair to fix fs/dax reference counting and changes
> >>> By Zi Yan (folio split changes), the series builds on top of those, but the
> >>> patches are not dependent on the folio split changes, IIRC
> >>>
> >>> Please do report bugs/issues that you come across.
> >>>
> >>> Balbir
> >>>
> >>
> >> Thanks for sharing. We used your series to experimentally enable THP migration
> >> of zone device pages in DRM GPU SVM and Xe. Here is an early draft [1] rebased
> >> on 6.16-rc1. It is still hacky but I wanted to share some findings/questions:
> >> - Is there an updated version of your series?
> > 
> > Here is a new one: https://lore.kernel.org/linux-mm/20250703233511.2028395-1-balbirs@nvidia.com/.
> 
> Thanks Zi!
> 
> Could you please try out the latest patches Francois?

Sure! Let me rebase and share results.

Francois