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Mon, 25 Mar 2024 08:21:05 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id iMOgGPEzAWZdHgAAD6G6ig (envelope-from ); Mon, 25 Mar 2024 08:21:05 +0000 From: Vlastimil Babka Date: Mon, 25 Mar 2024 09:20:32 +0100 Subject: [PATCH v2 1/2] mm, slab: move memcg charging to post-alloc hook MIME-Version: 1.0 Message-Id: <20240325-slab-memcg-v2-1-900a458233a6@suse.cz> References: <20240325-slab-memcg-v2-0-900a458233a6@suse.cz> In-Reply-To: <20240325-slab-memcg-v2-0-900a458233a6@suse.cz> To: Linus Torvalds , Josh Poimboeuf , Jeff Layton , Chuck Lever , Kees Cook , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Johannes Weiner , Michal Hocko , Muchun Song , Alexander Viro , Christian Brauner , Jan Kara , Shakeel Butt Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org, Vlastimil Babka , Chengming Zhou X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=10712; i=vbabka@suse.cz; h=from:subject:message-id; bh=euMCa5d5VUUeF8W9UqgWWtNYyJ+ULe5ZncwkAMI4uMY=; b=owEBbQGS/pANAwAIAbvgsHXSRYiaAcsmYgBmATPqJwFS6fIZ1mjjEmvOkVxte6JGZrD9lA0Wi QuJqKBoztKJATMEAAEIAB0WIQR7u8hBFZkjSJZITfG74LB10kWImgUCZgEz6gAKCRC74LB10kWI mv37B/0dztlTlEmEPLpyCpWq8pMACuW6aDrVkXxyxg7plY0ei1MuxVmcGaK/n5MrLcQKsH/1OoE bFovHHksBYmeYTRuVdVtgi0OdEI9RM3o9MS2eT6MHhoQaN0z36zlFcP3BLFjqmpLvXNo9diCoRo +x7ddobnFbNO2TnC7QxG8bK91zXAiHz+9xk9t7wTOoPuw82FRAKZbhh7ejhLbV9IBYCUf8VUuuW PZN6PNJqArcj0gF9Bgd4PU1UWsY7WpyFqbgkEJ2qkOZabV3O82y1TFIaKpgGzPfbBl5ThexMhgV bfLnO/bty35Dms0e0oz8+NVk2cSsumOVeNV8o8gR75Upru1f X-Developer-Key: i=vbabka@suse.cz; a=openpgp; fpr=A940D434992C2E8E99103D50224FA7E7CC82A664 X-Rspamd-Queue-Id: 0FEF8C0007 X-Rspam-User: X-Stat-Signature: sg4mqbt1esj7rsnjfuqc6ize8hfjpu78 X-Rspamd-Server: rspam03 X-HE-Tag: 1711354866-189344 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The MEMCG_KMEM integration with slab currently relies on two hooks during allocation. memcg_slab_pre_alloc_hook() determines the objcg and charges it, and memcg_slab_post_alloc_hook() assigns the objcg pointer to the allocated object(s). As Linus pointed out, this is unnecessarily complex. Failing to charge due to memcg limits should be rare, so we can optimistically allocate the object(s) and do the charging together with assigning the objcg pointer in a single post_alloc hook. In the rare case the charging fails, we can free the object(s) back. This simplifies the code (no need to pass around the objcg pointer) and potentially allows to separate charging from allocation in cases where it's common that the allocation would be immediately freed, and the memcg handling overhead could be saved. Suggested-by: Linus Torvalds Link: https://lore.kernel.org/all/CAHk-=whYOOdM7jWy5jdrAm8LxcgCMFyk2bt8fYYvZzM4U-zAQA@mail.gmail.com/ Reviewed-by: Roman Gushchin Reviewed-by: Chengming Zhou Signed-off-by: Vlastimil Babka Reported-by: Aishwarya TCV Signed-off-by: Vlastimil Babka Reviewed-by: Roman Gushchin Acked-by: Shakeel Butt --- mm/slub.c | 180 +++++++++++++++++++++++++++----------------------------------- 1 file changed, 77 insertions(+), 103 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 1bb2a93cf7b6..2440984503c8 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1887,23 +1887,36 @@ static inline size_t obj_full_size(struct kmem_cache *s) return s->size + sizeof(struct obj_cgroup *); } -/* - * Returns false if the allocation should fail. - */ -static bool __memcg_slab_pre_alloc_hook(struct kmem_cache *s, - struct list_lru *lru, - struct obj_cgroup **objcgp, - size_t objects, gfp_t flags) +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. */ - struct obj_cgroup *objcg = current_obj_cgroup(); + 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; @@ -1916,71 +1929,51 @@ static bool __memcg_slab_pre_alloc_hook(struct kmem_cache *s, return false; } - if (obj_cgroup_charge(objcg, flags, objects * obj_full_size(s))) + if (obj_cgroup_charge(objcg, flags, size * obj_full_size(s))) return false; - *objcgp = objcg; + 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; } -/* - * Returns false if the allocation should fail. - */ +static void memcg_alloc_abort_single(struct kmem_cache *s, void *object); + static __fastpath_inline -bool memcg_slab_pre_alloc_hook(struct kmem_cache *s, struct list_lru *lru, - struct obj_cgroup **objcgp, size_t objects, - gfp_t flags) +bool memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru, + gfp_t flags, size_t size, void **p) { - if (!memcg_kmem_online()) + if (likely(!memcg_kmem_online())) return true; if (likely(!(flags & __GFP_ACCOUNT) && !(s->flags & SLAB_ACCOUNT))) return true; - return likely(__memcg_slab_pre_alloc_hook(s, lru, objcgp, objects, - flags)); -} - -static void __memcg_slab_post_alloc_hook(struct kmem_cache *s, - struct obj_cgroup *objcg, - gfp_t flags, size_t size, - void **p) -{ - struct slab *slab; - unsigned long off; - size_t i; - - flags &= gfp_allowed_mask; - - for (i = 0; i < size; i++) { - if (likely(p[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; - } + if (likely(__memcg_slab_post_alloc_hook(s, lru, flags, size, p))) + return true; - 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)); - } else { - obj_cgroup_uncharge(objcg, obj_full_size(s)); - } + if (likely(size == 1)) { + memcg_alloc_abort_single(s, p); + *p = NULL; + } else { + kmem_cache_free_bulk(s, size, p); } -} - -static __fastpath_inline -void memcg_slab_post_alloc_hook(struct kmem_cache *s, struct obj_cgroup *objcg, - gfp_t flags, size_t size, void **p) -{ - if (likely(!memcg_kmem_online() || !objcg)) - return; - return __memcg_slab_post_alloc_hook(s, objcg, flags, size, p); + return false; } static void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, @@ -2019,44 +2012,23 @@ void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p, __memcg_slab_free_hook(s, slab, p, objects, objcgs); } - -static inline -void memcg_slab_alloc_error_hook(struct kmem_cache *s, int objects, - struct obj_cgroup *objcg) -{ - if (objcg) - obj_cgroup_uncharge(objcg, objects * obj_full_size(s)); -} #else /* CONFIG_MEMCG_KMEM */ static inline void memcg_free_slab_cgroups(struct slab *slab) { } -static inline bool memcg_slab_pre_alloc_hook(struct kmem_cache *s, - struct list_lru *lru, - struct obj_cgroup **objcgp, - size_t objects, gfp_t flags) -{ - return true; -} - -static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s, - struct obj_cgroup *objcg, +static inline bool memcg_slab_post_alloc_hook(struct kmem_cache *s, + struct list_lru *lru, gfp_t flags, size_t size, void **p) { + return true; } static inline void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p, int objects) { } - -static inline -void memcg_slab_alloc_error_hook(struct kmem_cache *s, int objects, - struct obj_cgroup *objcg) -{ -} #endif /* CONFIG_MEMCG_KMEM */ /* @@ -3736,10 +3708,7 @@ noinline int should_failslab(struct kmem_cache *s, gfp_t gfpflags) ALLOW_ERROR_INJECTION(should_failslab, ERRNO); static __fastpath_inline -struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, - struct list_lru *lru, - struct obj_cgroup **objcgp, - size_t size, gfp_t flags) +struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags) { flags &= gfp_allowed_mask; @@ -3748,14 +3717,11 @@ struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, if (unlikely(should_failslab(s, flags))) return NULL; - if (unlikely(!memcg_slab_pre_alloc_hook(s, lru, objcgp, size, flags))) - return NULL; - return s; } static __fastpath_inline -void slab_post_alloc_hook(struct kmem_cache *s, struct obj_cgroup *objcg, +bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru, gfp_t flags, size_t size, void **p, bool init, unsigned int orig_size) { @@ -3804,7 +3770,7 @@ void slab_post_alloc_hook(struct kmem_cache *s, struct obj_cgroup *objcg, kmsan_slab_alloc(s, p[i], init_flags); } - memcg_slab_post_alloc_hook(s, objcg, flags, size, p); + return memcg_slab_post_alloc_hook(s, lru, flags, size, p); } /* @@ -3821,10 +3787,9 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list gfp_t gfpflags, int node, unsigned long addr, size_t orig_size) { void *object; - struct obj_cgroup *objcg = NULL; bool init = false; - s = slab_pre_alloc_hook(s, lru, &objcg, 1, gfpflags); + s = slab_pre_alloc_hook(s, gfpflags); if (unlikely(!s)) return NULL; @@ -3841,8 +3806,10 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list /* * When init equals 'true', like for kzalloc() family, only * @orig_size bytes might be zeroed instead of s->object_size + * In case this fails due to memcg_slab_post_alloc_hook(), + * object is set to NULL */ - slab_post_alloc_hook(s, objcg, gfpflags, 1, &object, init, orig_size); + slab_post_alloc_hook(s, lru, gfpflags, 1, &object, init, orig_size); return object; } @@ -4281,6 +4248,16 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object, do_slab_free(s, slab, object, object, 1, addr); } +#ifdef CONFIG_MEMCG_KMEM +/* Do not inline the rare memcg charging failed path into the allocation path */ +static noinline +void memcg_alloc_abort_single(struct kmem_cache *s, void *object) +{ + if (likely(slab_free_hook(s, object, slab_want_init_on_free(s)))) + do_slab_free(s, virt_to_slab(object), object, object, 1, _RET_IP_); +} +#endif + static __fastpath_inline void slab_free_bulk(struct kmem_cache *s, struct slab *slab, void *head, void *tail, void **p, int cnt, unsigned long addr) @@ -4616,29 +4593,26 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, void **p) { int i; - struct obj_cgroup *objcg = NULL; if (!size) return 0; - /* memcg and kmem_cache debug support */ - s = slab_pre_alloc_hook(s, NULL, &objcg, size, flags); + s = slab_pre_alloc_hook(s, flags); if (unlikely(!s)) return 0; i = __kmem_cache_alloc_bulk(s, flags, size, p); + if (unlikely(i == 0)) + return 0; /* * memcg and kmem_cache debug support and memory initialization. * Done outside of the IRQ disabled fastpath loop. */ - if (likely(i != 0)) { - slab_post_alloc_hook(s, objcg, flags, size, p, - slab_want_init_on_alloc(flags, s), s->object_size); - } else { - memcg_slab_alloc_error_hook(s, size, objcg); + if (unlikely(!slab_post_alloc_hook(s, NULL, flags, size, p, + slab_want_init_on_alloc(flags, s), s->object_size))) { + return 0; } - return i; } EXPORT_SYMBOL(kmem_cache_alloc_bulk);