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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1698761358; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=71jccDuvmHUN0B2hAN0chVUZ3a/I3ZWuScusSDMRbZM=; b=EgWg7JyuljiAgmtHeNxZPVDCEzu19y0onJXhXs8aae8cO3ZMQHroKY26QyUFiFaebUhzCc RGV6bWjUO05MthcYp2hTuKmvk++h80PzPUQqKT6vJe0w3lTBc8M2DdpDA2JE+ug45MtF26 X/0C77Wy9EZYl/zFaNFqEn7aLM2cGT8= From: chengming.zhou@linux.dev To: vbabka@suse.cz, cl@linux.com, penberg@kernel.org, willy@infradead.org Cc: rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, chengming.zhou@linux.dev, Chengming Zhou Subject: [RFC PATCH v4 7/9] slub: Optimize deactivate_slab() Date: Tue, 31 Oct 2023 14:07:39 +0000 Message-Id: <20231031140741.79387-8-chengming.zhou@linux.dev> In-Reply-To: <20231031140741.79387-1-chengming.zhou@linux.dev> References: <20231031140741.79387-1-chengming.zhou@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 7656314001D X-Rspam-User: X-Stat-Signature: xx847z8h47t4bnfxd5p7izniabfcezx1 X-Rspamd-Server: rspam03 X-HE-Tag: 1698761359-308847 X-HE-Meta: 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 Salcq23C oRdvcQi92qBW7vOCldQtAxAQBaaSxwDlvgegjQNlVvh2TRahP+kC0qRBZroebq8TB1JKQK3Nlz1tKHMFijpsJ+PrigyRzxws578z9HMDdDGq2VlKX9unoAqxxCruFhTYE5mpougaxFqIrrfIhwDFRMUcwcWJGGhRQhA/rJqia+2Z7aLQuXDwGpNTBGYJbtTJsYxTFIUNy7fheOU1d49LZDd5WxcsSVFXNRU8GLZMtCyv81NcBknI4qkjxyS1YhC+eMw4Y 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: From: Chengming Zhou Since the introduce of unfrozen slabs on cpu partial list, we don't need to synchronize the slab frozen state under the node list_lock. The caller of deactivate_slab() and the caller of __slab_free() won't manipulate the slab list concurrently. So we can get node list_lock in the last stage if we really need to manipulate the slab list in this path. Signed-off-by: Chengming Zhou --- mm/slub.c | 76 +++++++++++++++++++------------------------------------ 1 file changed, 26 insertions(+), 50 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index bcb5b2c4e213..c429f8baba5f 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2468,10 +2468,8 @@ static void init_kmem_cache_cpus(struct kmem_cache *s) static void deactivate_slab(struct kmem_cache *s, struct slab *slab, void *freelist) { - enum slab_modes { M_NONE, M_PARTIAL, M_FREE, M_FULL_NOLIST }; struct kmem_cache_node *n = get_node(s, slab_nid(slab)); int free_delta = 0; - enum slab_modes mode = M_NONE; void *nextfree, *freelist_iter, *freelist_tail; int tail = DEACTIVATE_TO_HEAD; unsigned long flags = 0; @@ -2512,62 +2510,40 @@ static void deactivate_slab(struct kmem_cache *s, struct slab *slab, * * Ensure that the slab is unfrozen while the list presence * reflects the actual number of objects during unfreeze. - * - * We first perform cmpxchg holding lock and insert to list - * when it succeed. If there is mismatch then the slab is not - * unfrozen and number of objects in the slab may have changed. - * Then release lock and retry cmpxchg again. */ -redo: - - old.freelist = READ_ONCE(slab->freelist); - old.counters = READ_ONCE(slab->counters); - VM_BUG_ON(!old.frozen); - - /* Determine target state of the slab */ - new.counters = old.counters; - if (freelist_tail) { - new.inuse -= free_delta; - set_freepointer(s, freelist_tail, old.freelist); - new.freelist = freelist; - } else - new.freelist = old.freelist; - - new.frozen = 0; + do { + old.freelist = READ_ONCE(slab->freelist); + old.counters = READ_ONCE(slab->counters); + VM_BUG_ON(!old.frozen); + + /* Determine target state of the slab */ + new.counters = old.counters; + new.frozen = 0; + if (freelist_tail) { + new.inuse -= free_delta; + set_freepointer(s, freelist_tail, old.freelist); + new.freelist = freelist; + } else { + new.freelist = old.freelist; + } + } while (!slab_update_freelist(s, slab, + old.freelist, old.counters, + new.freelist, new.counters, + "unfreezing slab")); + /* + * Stage three: Manipulate the slab list based on the updated state. + */ if (!new.inuse && n->nr_partial >= s->min_partial) { - mode = M_FREE; + stat(s, DEACTIVATE_EMPTY); + discard_slab(s, slab); + stat(s, FREE_SLAB); } else if (new.freelist) { - mode = M_PARTIAL; - /* - * Taking the spinlock removes the possibility that - * acquire_slab() will see a slab that is frozen - */ spin_lock_irqsave(&n->list_lock, flags); - } else { - mode = M_FULL_NOLIST; - } - - - if (!slab_update_freelist(s, slab, - old.freelist, old.counters, - new.freelist, new.counters, - "unfreezing slab")) { - if (mode == M_PARTIAL) - spin_unlock_irqrestore(&n->list_lock, flags); - goto redo; - } - - - if (mode == M_PARTIAL) { add_partial(n, slab, tail); spin_unlock_irqrestore(&n->list_lock, flags); stat(s, tail); - } else if (mode == M_FREE) { - stat(s, DEACTIVATE_EMPTY); - discard_slab(s, slab); - stat(s, FREE_SLAB); - } else if (mode == M_FULL_NOLIST) { + } else { stat(s, DEACTIVATE_FULL); } } -- 2.20.1