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

[Zi Yan <ziy@nvidia.com>]

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/.

--
Best Regards,
Yan, Zi