Re: [PATCH 4/4] mm/mprotect: special-case small folios when applying write permissions

Lorenzo Stoakes (Oracle)
2026-03-20T10:42:26Z

On Fri, Mar 20, 2026 at 10:36:17AM +0000, Pedro Falcato wrote:
> On Thu, Mar 19, 2026 at 07:17:31PM +0000, Lorenzo Stoakes (Oracle) wrote:
> > On Thu, Mar 19, 2026 at 06:31:08PM +0000, Pedro Falcato wrote:
> > > The common order-0 case is important enough to want its own branch, and
> > > avoids the hairy, large loop logic that the CPU does not seem to handle
> > > particularly well.
> > >
> >
> > I think it'd be good to get a sense per-commit what the perf impact is.
>
> I added some numbers on the cover letter - this patch + the __always_inline
> one do the heavy lifting.

I mean again this makes me wonder if we shouldn't have some generalised batch
logic to handle order-0 cases.

>
> >
> > > Signed-off-by: Pedro Falcato <pfalcato@suse.de>
> >
> > I am iffy on the likely() in the same way I am always iffy on non-profile backed
> > likely()/unlikely() but this change seems sensible enough so:
> >
> > Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
>
> Thanks for the review!
>
> --
> Pedro