linux-kernel - Re: [PATCH v3] mm: slub: only warn once when allocating slab obj extensions fails

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Message-ID: <CAJuCfpGsrt=UrmvaWKX32w9_mYiDVgG6N-K_0F8aKs5dntOLog@mail.gmail.com>
Date: Mon, 2 Jun 2025 13:14:30 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Harry Yoo <harry.yoo@...cle.com>
Cc: Usama Arif <usamaarif642@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	hannes@...xchg.org, shakeel.butt@...ux.dev, vlad.wing@...il.com, 
	linux-mm@...ck.org, kent.overstreet@...ux.dev, cl@...two.org, 
	rientjes@...gle.com, vbabka@...e.cz, roman.gushchin@...ux.dev, 
	linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH v3] mm: slub: only warn once when allocating slab obj
 extensions fails

On Mon, May 26, 2025 at 3:05 AM Harry Yoo <harry.yoo@...cle.com> wrote:
>
> On Fri, May 23, 2025 at 05:52:40PM +0100, Usama Arif wrote:
> > In memory bound systems, a large number of warnings for failing this
> > allocation repeatedly may mask any real issues in the system
> > during memory pressure being reported in dmesg. Change this to
> > warning only once.
> >
> > Signed-off-by: Usama Arif <usamaarif642@...il.com>
> > Reported-by: Vlad Poenaru <vlad.wing@...il.com>
> > Closes: https://urldefense.com/v3/__https://lore.kernel.org/all/17fab2d6-5a74-4573-bcc3-b75951508f0a@gmail.com/__;!!ACWV5N9M2RV99hQ!Nv5xX_X4cBQR_HUDO6qfamxI0GEW1eFRCpPj29lANRashIUJDrEWAjU7vlys76FH0voShW07CjpDkzSST46Irg$
> > ---
>
> Acked-by: Harry Yoo <harry.yoo@...cle.com>

Acked-by: Suren Baghdasaryan <surenb@...gle.com>

>
> > v2 -> v3:
> > - Put warning back, but only warn once with pr_warn_once.
> > v1 -> v2:
> > - remove the warning completely. We will have a way in the
> >   future to indicate that the mem alloc profile is inaccurate.
> > ---
> >  mm/slub.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index dc9e729e1d26..36d7c43a6f2a 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -2102,10 +2102,12 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
> >
> >       slab = virt_to_slab(p);
> >       if (!slab_obj_exts(slab) &&
> > -         WARN(alloc_slab_obj_exts(slab, s, flags, false),
> > -              "%s, %s: Failed to create slab extension vector!\n",
> > -              __func__, s->name))
> > +         alloc_slab_obj_exts(slab, s, flags, false)) {
> > +             pr_warn_once("%s, %s: Failed to create slab extension vector!\n",
> > +                     __func__, s->name);
> >               return NULL;
> > +     }
> > +
> >
> >       return slab_obj_exts(slab) + obj_to_index(s, slab, p);
> >  }
> > --
> > 2.47.1
> >
>
> --
> Cheers,
> Harry / Hyeonggon