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bh=KdJtA4YoE6ORCzqq1AaRT5tX40ysKLrzxToE3yWrpNc=; b=9Bh+xb3bwIRXHzIn2wniiILwcrIoB8irmjGvkKTb7yikdN5thh/m6p+drBo7EMwbtJWjHG p5UrXNRUSFAvq8Bw== Received: from director2.suse.de ([192.168.254.72]) by imap3-int with ESMTPSA id 6EFaEniowGD6XgAALh3uQQ (envelope-from ); Wed, 09 Jun 2021 11:39:36 +0000 From: Vlastimil Babka To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim Cc: Sebastian Andrzej Siewior , Thomas Gleixner , Mel Gorman , Jesper Dangaard Brouer , Peter Zijlstra , Jann Horn , Vlastimil Babka Subject: [RFC v2 25/34] mm, slub: detach percpu partial list in unfreeze_partials() using this_cpu_cmpxchg() Date: Wed, 9 Jun 2021 13:38:54 +0200 Message-Id: <20210609113903.1421-26-vbabka@suse.cz> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210609113903.1421-1-vbabka@suse.cz> References: <20210609113903.1421-1-vbabka@suse.cz> MIME-Version: 1.0 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 16899E000240 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=eBbXi4Ck; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=9Bh+xb3b; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=eBbXi4Ck; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=9Bh+xb3b; spf=pass (imf21.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Stat-Signature: b3cmfom6tdigy18xbtwu5kpu86xm4jjs X-HE-Tag: 1623238771-473627 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: Instead of relying on disabled irqs for atomicity when detaching the percpu partial list, we can use this_cpu_cmpxchg() and detach without irqs disabled. However, unfreeze_partials() can be also called from another cpu on behalf of a cpu that is being offlined, so we need to restructure the code accordingly: - __unfreeze_partials() is the bulk of unfreeze_partials() that processes the detached percpu partial list - unfreeze_partials() uses this_cpu_cmpxchg() to detach list from current cpu - unfreeze_partials_cpu() is to be called for the offlined cpu so it needs no protection, and is called from __flush_cpu_slab() - flush_cpu_slab() is for the local cpu thus it needs to call unfreeze_partials(). So it can't simply call __flush_cpu_slab(smp_processor_id()) anymore and we have to open-code it Signed-off-by: Vlastimil Babka --- mm/slub.c | 77 +++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 55 insertions(+), 22 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 3e0ec7211d55..0867801e3086 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2287,25 +2287,15 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, } } -/* - * Unfreeze all the cpu partial slabs. - * - * This function must be called with preemption or migration - * disabled with c local to the cpu. - */ -static void unfreeze_partials(struct kmem_cache *s, - struct kmem_cache_cpu *c) -{ #ifdef CONFIG_SLUB_CPU_PARTIAL +static void __unfreeze_partials(struct kmem_cache *s, struct page *partial_page) +{ struct kmem_cache_node *n = NULL, *n2 = NULL; - struct page *page, *partial_page, *discard_page = NULL; + struct page *page, *discard_page = NULL; unsigned long flags; local_irq_save(flags); - partial_page = slub_percpu_partial(c); - c->partial = NULL; - while (partial_page) { struct page new; struct page old; @@ -2360,10 +2350,49 @@ static void unfreeze_partials(struct kmem_cache *s, discard_slab(s, page); stat(s, FREE_SLAB); } +} -#endif /* CONFIG_SLUB_CPU_PARTIAL */ +/* + * Unfreeze all the cpu partial slabs. + * + * This function must be called with preemption or migration + * disabled. + */ +static void unfreeze_partials(struct kmem_cache *s) +{ + struct page *partial_page; + + do { + partial_page = this_cpu_read(s->cpu_slab->partial); + + } while (partial_page && + this_cpu_cmpxchg(s->cpu_slab->partial, partial_page, NULL) + != partial_page); + + if (partial_page) + __unfreeze_partials(s, partial_page); } +static void unfreeze_partials_cpu(struct kmem_cache *s, + struct kmem_cache_cpu *c) +{ + struct page *partial_page; + + partial_page = slub_percpu_partial(c); + c->partial = NULL; + + if (partial_page) + __unfreeze_partials(s, partial_page); +} + +#else /* CONFIG_SLUB_CPU_PARTIAL */ + +static void unfreeze_partials(struct kmem_cache *s) { } +static void unfreeze_partials_cpu(struct kmem_cache *s, + struct kmem_cache_cpu *c) { } + +#endif /* CONFIG_SLUB_CPU_PARTIAL */ + /* * Put a page that was just frozen (in __slab_free|get_partial_node) into a * partial page slot if available. @@ -2392,7 +2421,7 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain) * partial array is full. Move the existing * set to the per node partial list. */ - unfreeze_partials(s, this_cpu_ptr(s->cpu_slab)); + unfreeze_partials(s); oldpage = NULL; pobjects = 0; pages = 0; @@ -2427,11 +2456,6 @@ static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c) stat(s, CPUSLAB_FLUSH); } -/* - * Flush cpu slab. - * - * Called from IPI handler with interrupts disabled. - */ static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu) { struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu); @@ -2439,14 +2463,23 @@ static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu) if (c->page) flush_slab(s, c); - unfreeze_partials(s, c); + unfreeze_partials_cpu(s, c); } +/* + * Flush cpu slab. + * + * Called from IPI handler with interrupts disabled. + */ static void flush_cpu_slab(void *d) { struct kmem_cache *s = d; + struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab); - __flush_cpu_slab(s, smp_processor_id()); + if (c->page) + flush_slab(s, c); + + unfreeze_partials(s); } static bool has_cpu_slab(int cpu, void *info)