linux-kernel - Re: [PATCH v5 23/37] mm/slab: add allocation accounting into slab allocation and free paths

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Date: Fri, 15 Mar 2024 11:58:52 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org
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Subject: Re: [PATCH v5 23/37] mm/slab: add allocation accounting into slab
 allocation and free paths

On 3/6/24 19:24, 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>
> Reviewed-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

Nit below:

> @@ -3833,6 +3913,7 @@ void slab_post_alloc_hook(struct kmem_cache *s,	struct obj_cgroup *objcg,
>  			  unsigned int orig_size)
>  {
>  	unsigned int zero_size = s->object_size;
> +	struct slabobj_ext *obj_exts;
>  	bool kasan_init = init;
>  	size_t i;
>  	gfp_t init_flags = flags & gfp_allowed_mask;
> @@ -3875,6 +3956,12 @@ 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 = 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 you could still do this a bit better:

Check mem_alloc_profiling_enabled() once before the whole block calling
prepare_slab_obj_exts_hook() and alloc_tag_add()
Remove need_slab_obj_ext() check from prepare_slab_obj_exts_hook()

>  	}
>  
>  	memcg_slab_post_alloc_hook(s, objcg, flags, size, p);
> @@ -4353,6 +4440,7 @@ 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);
>  
>  	if (likely(slab_free_hook(s, object, slab_want_init_on_free(s))))
>  		do_slab_free(s, slab, object, object, 1, addr);
> @@ -4363,6 +4451,7 @@ 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);
>  	/*
>  	 * With KASAN enabled slab_free_freelist_hook modifies the freelist
>  	 * to remove objects, whose reuse must be delayed.