linux-kernel - Re: [PATCH v3 21/35] mm/slab: add allocation accounting into slab allocation and free paths

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Date: Fri, 16 Feb 2024 11:38:59 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org, 
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Subject: Re: [PATCH v3 21/35] mm/slab: add allocation accounting into slab
 allocation and free paths

On Fri, Feb 16, 2024 at 05:31:11PM +0100, Vlastimil Babka wrote:
> On 2/12/24 22:39, Suren Baghdasaryan wrote:
> > Account slab allocations using codetag reference embedded into slabobj_ext.
> > 
> > Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
> > Co-developed-by: Kent Overstreet <kent.overstreet@...ux.dev>
> > Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
> > ---
> >  mm/slab.h | 26 ++++++++++++++++++++++++++
> >  mm/slub.c |  5 +++++
> >  2 files changed, 31 insertions(+)
> > 
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 224a4b2305fb..c4bd0d5348cb 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -629,6 +629,32 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_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)
> > +{
> > +	struct slabobj_ext *obj_exts;
> > +	int i;
> > +
> > +	obj_exts = slab_obj_exts(slab);
> > +	if (!obj_exts)
> > +		return;
> > +
> > +	for (i = 0; i < objects; i++) {
> > +		unsigned int off = 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 */
> 
> You don't actually use the alloc_tagging_slab_free_hook() anywhere? I see
> it's in the next patch, but logically should belong to this one.

I don't think it makes any sense to quibble about introducing something
in one patch that's not used until the next patch; often times, it's
just easier to review that way.