On 01.08.23 17:48, Peter Xu wrote:
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?
I thought about that, but decided against making that patch here more
complicated to eventually rip it again all out in #4.
I fully agree that FOLL_REMOTE does not make too much sense, but let's
rather keep it simple for this patch.
Thanks!
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.
Be prepared for my proposal of removing foll_flags from follow_page() ;)
(accompanied by a proper documentation)
Especially as we have FOLL_PIN users of FOLL_NOFAULT, follow_page() is a
bad fit.
--
Cheers,
David / dhildenb
