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From: Hao Li To: vbabka@kernel.org, harry@kernel.org Cc: akpm@linux-foundation.org, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slub: deduplicate NUMA policy calculation in allocation paths Message-ID: References: <20260618100913.346636-1-hao.li@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260618100913.346636-1-hao.li@linux.dev> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: x9zssj8ynhqnzg13wwyycjrua8diarrx X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 4D39D40017 X-HE-Tag: 1781796140-54997 X-HE-Meta: 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 QARqmRZf GmlphsTG8VwpL8A86nMKvQ5bNJRIyAz3AcdW8KF09k+coMtrdNaHuvbPQoRqFeNLRf12LdKjEqnC5oqPSnScc95TkbcIl0ngR0rDjWsaTBdHbKZ3PVOOpZHnv3u7BKgRPQGU65iC0fh8BAGx1b18JObwH+MaRFmf9mhd4smBbyjUjZVEbtXs7SaJpyO6BnUU1kpqDQSyYaeC/s1Q= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 18, 2026 at 06:08:52PM +0800, Hao Li wrote: > Currently, alloc_from_pcs() and __slab_alloc_node() both calculate the > NUMA policy independently. Since they are called consecutively in paths > like __kmalloc_nolock_noprof() and slab_alloc_node(), this leads to > redundant computations. > > Introduce a helper function to resolve the NUMA policy once, eliminating > the duplicated code and reducing execution overhead. > > Signed-off-by: Hao Li > --- > mm/slub.c | 72 ++++++++++++++++++++++--------------------------------- > 1 file changed, 29 insertions(+), 43 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 62e9cd46916f..45e9f379b7da 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -4523,32 +4523,36 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > return object; > } > > +static __always_inline int apply_numa_policy(int node) > +{ > +#ifdef CONFIG_NUMA > + if (static_branch_unlikely(&strict_numa) && > + node == NUMA_NO_NODE) { > + > + struct mempolicy *mpol = current->mempolicy; > + > + if (mpol) { > + /* > + * Special BIND rule support. If the local node > + * is in permitted set then do not redirect > + * to a particular node. > + * Otherwise we apply the memory policy to get > + * the node we need to allocate on. > + */ > + if (mpol->mode != MPOL_BIND || > + !node_isset(numa_mem_id(), mpol->nodes)) > + node = mempolicy_slab_node(); > + } > + } > +#endif > + return node; > +} > + > static void *__slab_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node, > const struct slab_alloc_context *ac) > { > void *object; > > -#ifdef CONFIG_NUMA > - if (static_branch_unlikely(&strict_numa) && > - node == NUMA_NO_NODE) { > - > - struct mempolicy *mpol = current->mempolicy; > - > - if (mpol) { > - /* > - * Special BIND rule support. If the local node > - * is in permitted set then do not redirect > - * to a particular node. > - * Otherwise we apply the memory policy to get > - * the node we need to allocate on. > - */ > - if (mpol->mode != MPOL_BIND || > - !node_isset(numa_mem_id(), mpol->nodes)) > - node = mempolicy_slab_node(); > - } > - } > -#endif > - > object = ___slab_alloc(s, gfpflags, node, ac); > > return object; oh!, __slab_alloc_node is almost an empty wrapper Maybe I need to eliminate it completely... > @@ -4756,28 +4760,6 @@ void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, unsigned int alloc_flags, > bool node_requested; > void *object; > > -#ifdef CONFIG_NUMA > - if (static_branch_unlikely(&strict_numa) && > - node == NUMA_NO_NODE) { > - > - struct mempolicy *mpol = current->mempolicy; > - > - if (mpol) { > - /* > - * Special BIND rule support. If the local node > - * is in permitted set then do not redirect > - * to a particular node. > - * Otherwise we apply the memory policy to get > - * the node we need to allocate on. > - */ > - if (mpol->mode != MPOL_BIND || > - !node_isset(numa_mem_id(), mpol->nodes)) > - > - node = mempolicy_slab_node(); > - } > - } > -#endif > - > node_requested = IS_ENABLED(CONFIG_NUMA) && node != NUMA_NO_NODE; > > /* > @@ -4927,6 +4909,8 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, > if (unlikely(object)) > goto out; > > + node = apply_numa_policy(node); > + > object = alloc_from_pcs(s, gfpflags, ac->alloc_flags, node); > > if (unlikely(!object)) > @@ -5430,6 +5414,8 @@ static void *__kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_f > */ > return NULL; > > + node = apply_numa_policy(node); > + > ret = alloc_from_pcs(s, gfp_flags, ac->alloc_flags, node); > if (ret) > goto success; > -- > 2.54.0 >