Re: [PATCH] mm: kvmalloc: make kmalloc fast path real fast path

Michal Hocko
2025-04-03T19:49:56Z

On Thu 03-04-25 09:21:50, Kees Cook wrote:
> On Thu, Apr 03, 2025 at 09:43:39AM +0200, Michal Hocko wrote:
[...]
> > mm/slub.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index b46f87662e71..2da40c2f6478 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -4972,14 +4972,16 @@ static gfp_t kmalloc_gfp_adjust(gfp_t flags, size_t size)
> > * We want to attempt a large physically contiguous block first because
> > * it is less likely to fragment multiple larger blocks and therefore
> > * contribute to a long term fragmentation less than vmalloc fallback.
> > - * However make sure that larger requests are not too disruptive - no
> > - * OOM killer and no allocation failure warnings as we have a fallback.
> > + * However make sure that larger requests are not too disruptive - i.e.
> > + * do not direct reclaim unless physically continuous memory is preferred
> > + * (__GFP_RETRY_MAYFAIL mode). We still kick in kswapd/kcompactd to start
> > + * working in the background but the allocation itself.
>
> I think a word is missing here? "...but do the allocation..." or
> "...allocation itself happens" ?

Thinking about this some more I would just cut this short and go with
"We still kick in kswapd/kcompactd to start working in the background"

Does that sound better?
--
Michal Hocko
SUSE Labs