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From: Suren Baghdasaryan <surenb@google.com>
Date: Tue, 27 Feb 2024 08:15:21 -0800
Message-ID: <CAJuCfpGvSfu5dtxFVxmQ4cMfQti2vGVtkNmm2kqQVPfrpFM1tw@mail.gmail.com>
Subject: Re: [PATCH v4 22/36] mm/slab: add allocation accounting into slab
 allocation and free paths
To: Vlastimil Babka <vbabka@suse.cz>
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On Tue, Feb 27, 2024 at 5:07=E2=80=AFAM Vlastimil Babka <vbabka@suse.cz> wr=
ote:
>
>
>
> On 2/21/24 20:40, Suren Baghdasaryan wrote:
> > Account slab allocations using codetag reference embedded into slabobj_=
ext.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>
> > Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> > ---
> >  mm/slab.h | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  mm/slub.c |  9 ++++++++
> >  2 files changed, 75 insertions(+)
> >
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 13b6ba2abd74..c4bd0d5348cb 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -567,6 +567,46 @@ static inline struct slabobj_ext *slab_obj_exts(st=
ruct slab *slab)
> >  int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
> >                       gfp_t gfp, bool new_slab);
> >
> > +static inline bool need_slab_obj_ext(void)
> > +{
> > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > +     if (mem_alloc_profiling_enabled())
> > +             return true;
> > +#endif
> > +     /*
> > +      * CONFIG_MEMCG_KMEM creates vector of obj_cgroup objects conditi=
onally
> > +      * inside memcg_slab_post_alloc_hook. No other users for now.
> > +      */
> > +     return false;
> > +}
> > +
> > +static inline struct slabobj_ext *
> > +prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
> > +{
> > +     struct slab *slab;
> > +
> > +     if (!p)
> > +             return NULL;
> > +
> > +     if (!need_slab_obj_ext())
> > +             return NULL;
> > +
> > +     if (s->flags & SLAB_NO_OBJ_EXT)
> > +             return NULL;
> > +
> > +     if (flags & __GFP_NO_OBJ_EXT)
> > +             return NULL;
> > +
> > +     slab =3D 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))
> > +             return NULL;
> > +
> > +     return slab_obj_exts(slab) + obj_to_index(s, slab, p);
> > +}
> > +
> >  #else /* CONFIG_SLAB_OBJ_EXT */
> >
> >  static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)
> > @@ -589,6 +629,32 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, g=
fp_t flags, void *p)
> >
> >  #endif /* CONFIG_SLAB_OBJ_EXT */
> >
> > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > +
> > +static inline void alloc_tagging_slab_free_hook(struct kmem_cache *s, =
struct slab *slab,
> > +                                     void **p, int objects)
>
> Only used from mm/slub.c so could move?

Ack.

>
> > +{
> > +     struct slabobj_ext *obj_exts;
> > +     int i;
> > +
> > +     obj_exts =3D slab_obj_exts(slab);
> > +     if (!obj_exts)
> > +             return;
> > +
> > +     for (i =3D 0; i < objects; i++) {
> > +             unsigned int off =3D obj_to_index(s, slab, p[i]);
> > +
> > +             alloc_tag_sub(&obj_exts[off].ref, s->size);
> > +     }
> > +}
> > +
> > +#else
> > +
> > +static inline void alloc_tagging_slab_free_hook(struct kmem_cache *s, =
struct slab *slab,
> > +                                     void **p, int objects) {}
> > +
> > +#endif /* CONFIG_MEM_ALLOC_PROFILING */
> > +
> >  #ifdef CONFIG_MEMCG_KMEM
> >  void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgd=
at,
> >                    enum node_stat_item idx, int nr);
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 5dc7beda6c0d..a69b6b4c8df6 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -3826,6 +3826,7 @@ void slab_post_alloc_hook(struct kmem_cache *s, s=
truct obj_cgroup *objcg,
> >                         unsigned int orig_size)
> >  {
> >       unsigned int zero_size =3D s->object_size;
> > +     struct slabobj_ext *obj_exts;
> >       bool kasan_init =3D init;
> >       size_t i;
> >       gfp_t init_flags =3D flags & gfp_allowed_mask;
> > @@ -3868,6 +3869,12 @@ void slab_post_alloc_hook(struct kmem_cache *s, =
       struct obj_cgroup *objcg,
> >               kmemleak_alloc_recursive(p[i], s->object_size, 1,
> >                                        s->flags, init_flags);
> >               kmsan_slab_alloc(s, p[i], init_flags);
> > +             obj_exts =3D prepare_slab_obj_exts_hook(s, flags, p[i]);
> > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > +             /* obj_exts can be allocated for other reasons */
> > +             if (likely(obj_exts) && mem_alloc_profiling_enabled())
> > +                     alloc_tag_add(&obj_exts->ref, current->alloc_tag,=
 s->size);
> > +#endif
>
> I think that like in the page allocator, this could be better guarded by
> mem_alloc_profiling_enabled() as the outermost thing.

Oops, missed it. Will fix.

>
> >       }
> >
> >       memcg_slab_post_alloc_hook(s, objcg, flags, size, p);
> > @@ -4346,6 +4353,7 @@ void slab_free(struct kmem_cache *s, struct slab =
*slab, void *object,
> >              unsigned long addr)
> >  {
> >       memcg_slab_free_hook(s, slab, &object, 1);
> > +     alloc_tagging_slab_free_hook(s, slab, &object, 1);
>
> Same here, the static key is not even inside of this?

Ack.

>
> >
> >       if (likely(slab_free_hook(s, object, slab_want_init_on_free(s))))
> >               do_slab_free(s, slab, object, object, 1, addr);
> > @@ -4356,6 +4364,7 @@ void slab_free_bulk(struct kmem_cache *s, struct =
slab *slab, void *head,
> >                   void *tail, void **p, int cnt, unsigned long addr)
> >  {
> >       memcg_slab_free_hook(s, slab, p, cnt);
> > +     alloc_tagging_slab_free_hook(s, slab, p, cnt);
>
> Ditto.

Ack.

>
> >       /*
> >        * With KASAN enabled slab_free_freelist_hook modifies the freeli=
st
> >        * to remove objects, whose reuse must be delayed.
>
> --
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