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[146.241.69.130]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42caeb43d73sm105918415e9.24.2024.09.10.01.26.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Sep 2024 01:26:38 -0700 (PDT) Message-ID: <5d48fe26-1e18-4941-99d4-8c03e83f5e76@redhat.com> Date: Tue, 10 Sep 2024 10:26:36 +0200 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Paolo Abeni Subject: Re: [PATCH v4] memcg: add charging of already allocated slab objects To: Shakeel Butt , Andrew Morton , Vlastimil Babka Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , David Rientjes , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Eric Dumazet , "David S . Miller" , Jakub Kicinski , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Meta kernel team , cgroups@vger.kernel.org, netdev@vger.kernel.org References: <20240905173422.1565480-1-shakeel.butt@linux.dev> Content-Language: en-US In-Reply-To: <20240905173422.1565480-1-shakeel.butt@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/5/24 19:34, Shakeel Butt wrote: > At the moment, the slab objects are charged to the memcg at the > allocation time. However there are cases where slab objects are > allocated at the time where the right target memcg to charge it to is > not known. One such case is the network sockets for the incoming > connection which are allocated in the softirq context. > > Couple hundred thousand connections are very normal on large loaded > server and almost all of those sockets underlying those connections get > allocated in the softirq context and thus not charged to any memcg. > However later at the accept() time we know the right target memcg to > charge. Let's add new API to charge already allocated objects, so we can > have better accounting of the memory usage. > > To measure the performance impact of this change, tcp_crr is used from > the neper [1] performance suite. Basically it is a network ping pong > test with new connection for each ping pong. > > The server and the client are run inside 3 level of cgroup hierarchy > using the following commands: > > Server: > $ tcp_crr -6 > > Client: > $ tcp_crr -6 -c -H ${server_ip} > > If the client and server run on different machines with 50 GBPS NIC, > there is no visible impact of the change. > > For the same machine experiment with v6.11-rc5 as base. > > base (throughput) with-patch > tcp_crr 14545 (+- 80) 14463 (+- 56) > > It seems like the performance impact is within the noise. > > Link: https://github.com/google/neper [1] > Signed-off-by: Shakeel Butt > Reviewed-by: Roman Gushchin > --- > v3: https://lore.kernel.org/all/20240829175339.2424521-1-shakeel.butt@linux.dev/ > Changes since v3: > - Add kernel doc for kmem_cache_charge. > > v2: https://lore.kernel.org/all/20240827235228.1591842-1-shakeel.butt@linux.dev/ > Change since v2: > - Add handling of already charged large kmalloc objects. > - Move the normal kmalloc cache check into a function. > > v1: https://lore.kernel.org/all/20240826232908.4076417-1-shakeel.butt@linux.dev/ > Changes since v1: > - Correctly handle large allocations which bypass slab > - Rearrange code to avoid compilation errors for !CONFIG_MEMCG builds > > RFC: https://lore.kernel.org/all/20240824010139.1293051-1-shakeel.butt@linux.dev/ > Changes since the RFC: > - Added check for already charged slab objects. > - Added performance results from neper's tcp_crr > > > include/linux/slab.h | 20 ++++++++++++++ > mm/slab.h | 7 +++++ > mm/slub.c | 49 +++++++++++++++++++++++++++++++++ > net/ipv4/inet_connection_sock.c | 5 ++-- > 4 files changed, 79 insertions(+), 2 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index eb2bf4629157..68789c79a530 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -547,6 +547,26 @@ void *kmem_cache_alloc_lru_noprof(struct kmem_cache *s, struct list_lru *lru, > gfp_t gfpflags) __assume_slab_alignment __malloc; > #define kmem_cache_alloc_lru(...) alloc_hooks(kmem_cache_alloc_lru_noprof(__VA_ARGS__)) > > +/** > + * kmem_cache_charge - memcg charge an already allocated slab memory > + * @objp: address of the slab object to memcg charge. > + * @gfpflags: describe the allocation context > + * > + * kmem_cache_charge is the normal method to charge a slab object to the current > + * memcg. The objp should be pointer returned by the slab allocator functions > + * like kmalloc or kmem_cache_alloc. The memcg charge behavior can be controller > + * through gfpflags parameter. > + * > + * There are several cases where it will return true regardless. More > + * specifically: > + * > + * 1. For !CONFIG_MEMCG or cgroup_disable=memory systems. > + * 2. Already charged slab objects. > + * 3. For slab objects from KMALLOC_NORMAL caches. > + * > + * Return: true if charge was successful otherwise false. > + */ > +bool kmem_cache_charge(void *objp, gfp_t gfpflags); > void kmem_cache_free(struct kmem_cache *s, void *objp); > > kmem_buckets *kmem_buckets_create(const char *name, slab_flags_t flags, > diff --git a/mm/slab.h b/mm/slab.h > index dcdb56b8e7f5..9f907e930609 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -443,6 +443,13 @@ static inline bool is_kmalloc_cache(struct kmem_cache *s) > return (s->flags & SLAB_KMALLOC); > } > > +static inline bool is_kmalloc_normal(struct kmem_cache *s) > +{ > + if (!is_kmalloc_cache(s)) > + return false; > + return !(s->flags & (SLAB_CACHE_DMA|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT)); > +} > + > /* Legal flag mask for kmem_cache_create(), for various configurations */ > #define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | \ > SLAB_CACHE_DMA32 | SLAB_PANIC | \ > diff --git a/mm/slub.c b/mm/slub.c > index c9d8a2497fd6..3f2a89f7a23a 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2185,6 +2185,41 @@ void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p, > > __memcg_slab_free_hook(s, slab, p, objects, obj_exts); > } > + > +static __fastpath_inline > +bool memcg_slab_post_charge(void *p, gfp_t flags) > +{ > + struct slabobj_ext *slab_exts; > + struct kmem_cache *s; > + struct folio *folio; > + struct slab *slab; > + unsigned long off; > + > + folio = virt_to_folio(p); > + if (!folio_test_slab(folio)) { > + return folio_memcg_kmem(folio) || > + (__memcg_kmem_charge_page(folio_page(folio, 0), flags, > + folio_order(folio)) == 0); > + } > + > + slab = folio_slab(folio); > + s = slab->slab_cache; > + > + /* Ignore KMALLOC_NORMAL cache to avoid circular dependency. */ > + if (is_kmalloc_normal(s)) > + return true; > + > + /* Ignore already charged objects. */ > + slab_exts = slab_obj_exts(slab); > + if (slab_exts) { > + off = obj_to_index(s, slab, p); > + if (unlikely(slab_exts[off].objcg)) > + return true; > + } > + > + return __memcg_slab_post_alloc_hook(s, NULL, flags, 1, &p); > +} > + > #else /* CONFIG_MEMCG */ > static inline bool memcg_slab_post_alloc_hook(struct kmem_cache *s, > struct list_lru *lru, > @@ -2198,6 +2233,11 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, > void **p, int objects) > { > } > + > +static inline bool memcg_slab_post_charge(void *p, gfp_t flags) > +{ > + return true; > +} > #endif /* CONFIG_MEMCG */ > > /* > @@ -4062,6 +4102,15 @@ void *kmem_cache_alloc_lru_noprof(struct kmem_cache *s, struct list_lru *lru, > } > EXPORT_SYMBOL(kmem_cache_alloc_lru_noprof); > > +bool kmem_cache_charge(void *objp, gfp_t gfpflags) > +{ > + if (!memcg_kmem_online()) > + return true; > + > + return memcg_slab_post_charge(objp, gfpflags); > +} > +EXPORT_SYMBOL(kmem_cache_charge); > + > /** > * kmem_cache_alloc_node - Allocate an object on the specified node > * @s: The cache to allocate from. > diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c > index 64d07b842e73..3c13ca8c11fb 100644 > --- a/net/ipv4/inet_connection_sock.c > +++ b/net/ipv4/inet_connection_sock.c > @@ -715,6 +715,7 @@ struct sock *inet_csk_accept(struct sock *sk, struct proto_accept_arg *arg) > release_sock(sk); > if (newsk && mem_cgroup_sockets_enabled) { > int amt = 0; > + gfp_t gfp = GFP_KERNEL | __GFP_NOFAIL; > > /* atomically get the memory usage, set and charge the > * newsk->sk_memcg. > @@ -731,8 +732,8 @@ struct sock *inet_csk_accept(struct sock *sk, struct proto_accept_arg *arg) > } > > if (amt) > - mem_cgroup_charge_skmem(newsk->sk_memcg, amt, > - GFP_KERNEL | __GFP_NOFAIL); > + mem_cgroup_charge_skmem(newsk->sk_memcg, amt, gfp); > + kmem_cache_charge(newsk, gfp); > > release_sock(newsk); > } The networking bits looks sane to me - with a very minor nit about the reverse xmas tree order in variables declaration above. Acked-by: Paolo Abeni