Re: [PATCH v2 1/8] mm/gup: reintroduce FOLL_NUMA as FOLL_HONOR_NUMA_FAULT

Peter Xu
2023-08-01T15:48:57Z

On Tue, Aug 01, 2023 at 02:48:37PM +0200, David Hildenbrand wrote:
> @@ -2240,6 +2244,12 @@ static bool is_valid_gup_args(struct page **pages, int *locked,
> gup_flags |= FOLL_UNLOCKABLE;
> }
>
> + /*
> + * For now, always trigger NUMA hinting faults. Some GUP users like
> + * KVM really require it to benefit from autonuma.
> + */
> + gup_flags |= FOLL_HONOR_NUMA_FAULT;

Since at it, do we want to not set it for FOLL_REMOTE, which still sounds
like a good thing to have?

Other than that, looks good here.

Side note: when I was looking at the flags again just to check the
interactions over numa balancing, I found FOLL_NOFAULT and I highly suspect
that's not needed, instead it just wants to use follow_page[_mask]() with
some proper gup flags passed over.. but that's off topic.

Thanks,

--
Peter Xu