Re: [PATCH RFC 2/4] mm, slab: move slab_memcg hooks to mm/memcontrol.c

Roman Gushchin
2024-03-12T18:56:39Z

On Fri, Mar 01, 2024 at 06:07:09PM +0100, Vlastimil Babka wrote:
> The hooks make multiple calls to functions in mm/memcontrol.c, including
> to th current_obj_cgroup() marked __always_inline. It might be faster to
> make a single call to the hook in mm/memcontrol.c instead. The hooks
> also don't use almost anything from mm/slub.c. obj_full_size() can move
> with the hooks and cache_vmstat_idx() to the internal mm/slab.h
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/memcontrol.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++
> mm/slab.h | 10 ++++++
> mm/slub.c | 100 --------------------------------------------------------
> 3 files changed, 100 insertions(+), 100 deletions(-)

Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>

Btw, even before your change:
$ cat mm/memcontrol.c | wc -l
8318
so I wonder if soon we might want to split it into some smaller parts.

Thanks!

>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e4c8735e7c85..37ee9356a26c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3575,6 +3575,96 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
> refill_obj_stock(objcg, size, true);
> }
>
> +static inline size_t obj_full_size(struct kmem_cache *s)
> +{
> + /*
> + * For each accounted object there is an extra space which is used
> + * to store obj_cgroup membership. Charge it too.
> + */
> + return s->size + sizeof(struct obj_cgroup *);
> +}
> +
> +bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
> + gfp_t flags, size_t size, void **p)
> +{
> + struct obj_cgroup *objcg;
> + struct slab *slab;
> + unsigned long off;
> + size_t i;
> +
> + /*
> + * The obtained objcg pointer is safe to use within the current scope,
> + * defined by current task or set_active_memcg() pair.
> + * obj_cgroup_get() is used to get a permanent reference.
> + */
> + objcg = current_obj_cgroup();
> + if (!objcg)
> + return true;
> +
> + /*
> + * slab_alloc_node() avoids the NULL check, so we might be called with a
> + * single NULL object. kmem_cache_alloc_bulk() aborts if it can't fill
> + * the whole requested size.
> + * return success as there's nothing to free back
> + */
> + if (unlikely(*p == NULL))
> + return true;
> +
> + flags &= gfp_allowed_mask;
> +
> + if (lru) {
> + int ret;
> + struct mem_cgroup *memcg;
> +
> + memcg = get_mem_cgroup_from_objcg(objcg);
> + ret = memcg_list_lru_alloc(memcg, lru, flags);
> + css_put(&memcg->css);
> +
> + if (ret)
> + return false;
> + }
> +
> + if (obj_cgroup_charge(objcg, flags, size * obj_full_size(s)))
> + return false;
> +
> + for (i = 0; i < size; i++) {
> + slab = virt_to_slab(p[i]);
> +
> + if (!slab_objcgs(slab) &&
> + memcg_alloc_slab_cgroups(slab, s, flags, false)) {
> + obj_cgroup_uncharge(objcg, obj_full_size(s));
> + continue;
> + }
> +
> + off = obj_to_index(s, slab, p[i]);
> + obj_cgroup_get(objcg);
> + slab_objcgs(slab)[off] = objcg;
> + mod_objcg_state(objcg, slab_pgdat(slab),
> + cache_vmstat_idx(s), obj_full_size(s));
> + }
> +
> + return true;
> +}
> +
> +void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
> + void **p, int objects, struct obj_cgroup **objcgs)
> +{
> + for (int i = 0; i < objects; i++) {
> + struct obj_cgroup *objcg;
> + unsigned int off;
> +
> + off = obj_to_index(s, slab, p[i]);
> + objcg = objcgs[off];
> + if (!objcg)
> + continue;
> +
> + objcgs[off] = NULL;
> + obj_cgroup_uncharge(objcg, obj_full_size(s));
> + mod_objcg_state(objcg, slab_pgdat(slab), cache_vmstat_idx(s),
> + -obj_full_size(s));
> + obj_cgroup_put(objcg);
> + }
> +}
> #endif /* CONFIG_MEMCG_KMEM */
>
> /*
> diff --git a/mm/slab.h b/mm/slab.h
> index 54deeb0428c6..3f170673fa55 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -541,6 +541,12 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla
> return false;
> }
>
> +static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache *s)
> +{
> + return (s->flags & SLAB_RECLAIM_ACCOUNT) ?
> + NR_SLAB_RECLAIMABLE_B : NR_SLAB_UNRECLAIMABLE_B;
> +}
> +
> #ifdef CONFIG_MEMCG_KMEM
> /*
> * slab_objcgs - get the object cgroups vector associated with a slab
> @@ -564,6 +570,10 @@ int memcg_alloc_slab_cgroups(struct slab *slab, struct kmem_cache *s,
> gfp_t gfp, bool new_slab);
> void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
> enum node_stat_item idx, int nr);
> +bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
> + gfp_t flags, size_t size, void **p);
> +void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
> + void **p, int objects, struct obj_cgroup **objcgs);
> #else /* CONFIG_MEMCG_KMEM */
> static inline struct obj_cgroup **slab_objcgs(struct slab *slab)
> {
> diff --git a/mm/slub.c b/mm/slub.c
> index 7022a1246bab..64da169d672a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1875,12 +1875,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct slab *slab,
> #endif
> #endif /* CONFIG_SLUB_DEBUG */
>
> -static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache *s)
> -{
> - return (s->flags & SLAB_RECLAIM_ACCOUNT) ?
> - NR_SLAB_RECLAIMABLE_B : NR_SLAB_UNRECLAIMABLE_B;
> -}
> -
> #ifdef CONFIG_MEMCG_KMEM
> static inline void memcg_free_slab_cgroups(struct slab *slab)
> {
> @@ -1888,79 +1882,6 @@ static inline void memcg_free_slab_cgroups(struct slab *slab)
> slab->memcg_data = 0;
> }
>
> -static inline size_t obj_full_size(struct kmem_cache *s)
> -{
> - /*
> - * For each accounted object there is an extra space which is used
> - * to store obj_cgroup membership. Charge it too.
> - */
> - return s->size + sizeof(struct obj_cgroup *);
> -}
> -
> -static bool __memcg_slab_post_alloc_hook(struct kmem_cache *s,
> - struct list_lru *lru,
> - gfp_t flags, size_t size,
> - void **p)
> -{
> - struct obj_cgroup *objcg;
> - struct slab *slab;
> - unsigned long off;
> - size_t i;
> -
> - /*
> - * The obtained objcg pointer is safe to use within the current scope,
> - * defined by current task or set_active_memcg() pair.
> - * obj_cgroup_get() is used to get a permanent reference.
> - */
> - objcg = current_obj_cgroup();
> - if (!objcg)
> - return true;
> -
> - /*
> - * slab_alloc_node() avoids the NULL check, so we might be called with a
> - * single NULL object. kmem_cache_alloc_bulk() aborts if it can't fill
> - * the whole requested size.
> - * return success as there's nothing to free back
> - */
> - if (unlikely(*p == NULL))
> - return true;
> -
> - flags &= gfp_allowed_mask;
> -
> - if (lru) {
> - int ret;
> - struct mem_cgroup *memcg;
> -
> - memcg = get_mem_cgroup_from_objcg(objcg);
> - ret = memcg_list_lru_alloc(memcg, lru, flags);
> - css_put(&memcg->css);
> -
> - if (ret)
> - return false;
> - }
> -
> - if (obj_cgroup_charge(objcg, flags, size * obj_full_size(s)))
> - return false;
> -
> - for (i = 0; i < size; i++) {
> - slab = virt_to_slab(p[i]);
> -
> - if (!slab_objcgs(slab) &&
> - memcg_alloc_slab_cgroups(slab, s, flags, false)) {
> - obj_cgroup_uncharge(objcg, obj_full_size(s));
> - continue;
> - }
> -
> - off = obj_to_index(s, slab, p[i]);
> - obj_cgroup_get(objcg);
> - slab_objcgs(slab)[off] = objcg;
> - mod_objcg_state(objcg, slab_pgdat(slab),
> - cache_vmstat_idx(s), obj_full_size(s));
> - }
> -
> - return true;
> -}
> -
> static void memcg_alloc_abort_single(struct kmem_cache *s, void *object);
>
> static __fastpath_inline
> @@ -1986,27 +1907,6 @@ bool memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
> return false;
> }
>
> -static void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
> - void **p, int objects,
> - struct obj_cgroup **objcgs)
> -{
> - for (int i = 0; i < objects; i++) {
> - struct obj_cgroup *objcg;
> - unsigned int off;
> -
> - off = obj_to_index(s, slab, p[i]);
> - objcg = objcgs[off];
> - if (!objcg)
> - continue;
> -
> - objcgs[off] = NULL;
> - obj_cgroup_uncharge(objcg, obj_full_size(s));
> - mod_objcg_state(objcg, slab_pgdat(slab), cache_vmstat_idx(s),
> - -obj_full_size(s));
> - obj_cgroup_put(objcg);
> - }
> -}
> -
> static __fastpath_inline
> void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
> int objects)
>
> --
> 2.44.0
>
>