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Thu, 18 Jan 2024 19:53:18 -0800 (PST) Received: from [10.254.224.1] ([139.177.225.241]) by smtp.gmail.com with ESMTPSA id pd5-20020a17090b1dc500b0028c5585fb41sm2705415pjb.45.2024.01.18.19.53.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Jan 2024 19:53:18 -0800 (PST) Message-ID: Date: Fri, 19 Jan 2024 11:53:12 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] mm/slub: directly load freelist from cpu partial slab in the likely case Content-Language: en-US To: "Christoph Lameter (Ampere)" Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Joonsoo Kim , Vlastimil Babka , Pekka Enberg , Andrew Morton , Roman Gushchin , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240117-slab-misc-v1-0-fd1c49ccbe70@bytedance.com> <20240117-slab-misc-v1-1-fd1c49ccbe70@bytedance.com> <76641777-1918-2b29-b6aa-bda9b5467aa3@gentwo.org> <412b8618-0941-4d9d-85df-ee480695e7f7@bytedance.com> From: Chengming Zhou In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2024/1/19 06:14, Christoph Lameter (Ampere) wrote: > On Thu, 18 Jan 2024, Chengming Zhou wrote: > >> So get_freelist() has two cases to handle: cpu slab and cpu partial list slab. >> The latter is NOT frozen, so need to remove "VM_BUG_ON(!new.frozen)" from it. > > Right so keep the check if it is the former? > Ok, I get it. Maybe like this: diff --git a/mm/slub.c b/mm/slub.c index 2ef88bbf56a3..7fa9dbc2e938 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3313,7 +3313,7 @@ __update_cpu_freelist_fast(struct kmem_cache *s, * * If this function returns NULL then the slab has been unfrozen. */ -static inline void *get_freelist(struct kmem_cache *s, struct slab *slab) +static inline void *get_freelist(struct kmem_cache *s, struct slab *slab, int frozen) { struct slab new; unsigned long counters; @@ -3326,7 +3326,7 @@ static inline void *get_freelist(struct kmem_cache *s, struct slab *slab) counters = slab->counters; new.counters = counters; - VM_BUG_ON(!new.frozen); + VM_BUG_ON(frozen && !new.frozen); new.inuse = slab->objects; new.frozen = freelist != NULL; @@ -3440,7 +3440,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, if (freelist) goto load_freelist; - freelist = get_freelist(s, slab); + freelist = get_freelist(s, slab, 1); if (!freelist) { c->slab = NULL; @@ -3498,18 +3498,19 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, slab = slub_percpu_partial(c); slub_set_percpu_partial(c, slab); - local_unlock_irqrestore(&s->cpu_slab->lock, flags); - stat(s, CPU_PARTIAL_ALLOC); - if (unlikely(!node_match(slab, node) || - !pfmemalloc_match(slab, gfpflags))) { - slab->next = NULL; - __put_partials(s, slab); - continue; + if (likely(node_match(slab, node) && + pfmemalloc_match(slab, gfpflags))) { + c->slab = slab; + freelist = get_freelist(s, slab, 0); + stat(s, CPU_PARTIAL_ALLOC); + goto load_freelist; } - freelist = freeze_slab(s, slab); - goto retry_load_slab; + local_unlock_irqrestore(&s->cpu_slab->lock, flags); + + slab->next = NULL; + __put_partials(s, slab); } #endif