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h=from:from:reply-to: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=YNHpFI9YeegQ7Tr0mlUdnFpfRtuVDo5qh+/Of6eaUa4=; b=boZOzaqYnsU20KZW32qh3fuG1Xcy8cEdcH25QA3QPNUoJl3JOnLGYdzH0UW4v29PksIgiO rbmUUDuRTO+vFZBg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 9B16813BE1; Mon, 23 Aug 2021 14:58:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id CH9TJaK3I2EFQQAAMHmgww (envelope-from ); Mon, 23 Aug 2021 14:58:42 +0000 From: Vlastimil Babka To: Andrew Morton , Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Galbraith , Sebastian Andrzej Siewior , Thomas Gleixner , Mel Gorman , Jesper Dangaard Brouer , Jann Horn , Vlastimil Babka Subject: [PATCH v5 29/35] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context Date: Mon, 23 Aug 2021 16:58:20 +0200 Message-Id: <20210823145826.3857-30-vbabka@suse.cz> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210823145826.3857-1-vbabka@suse.cz> References: <20210823145826.3857-1-vbabka@suse.cz> MIME-Version: 1.0 Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=NnTavDNb; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=boZOzaqY; spf=pass (imf14.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C71526001993 X-Stat-Signature: ci6foadhg8uejtge4ur5mcniseqbe7by X-HE-Tag: 1629730723-294148 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: From: Sebastian Andrzej Siewior flush_all() flushes a specific SLAB cache on each CPU (where the cache is present). The deactivate_slab()/__free_slab() invocation happens within IPI handler and is problematic for PREEMPT_RT. The flush operation is not a frequent operation or a hot path. The per-CPU flush operation can be moved to within a workqueue. [vbabka@suse.cz: adapt to new SLUB changes] Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Vlastimil Babka --- mm/slab_common.c | 2 ++ mm/slub.c | 79 ++++++++++++++++++++++++++++++++++++++++-------- 2 files changed, 68 insertions(+), 13 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index 1c673c323baf..ec2bb0beed75 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -502,6 +502,7 @@ void kmem_cache_destroy(struct kmem_cache *s) if (unlikely(!s)) return; + cpus_read_lock(); mutex_lock(&slab_mutex); s->refcount--; @@ -516,6 +517,7 @@ void kmem_cache_destroy(struct kmem_cache *s) } out_unlock: mutex_unlock(&slab_mutex); + cpus_read_unlock(); } EXPORT_SYMBOL(kmem_cache_destroy); diff --git a/mm/slub.c b/mm/slub.c index bb7e05543738..29d71ae20c90 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2516,33 +2516,79 @@ static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu) unfreeze_partials_cpu(s, c); } +struct slub_flush_work { + struct work_struct work; + struct kmem_cache *s; + bool skip; +}; + /* * Flush cpu slab. * - * Called from IPI handler with interrupts disabled. + * Called from CPU work handler with migration disabled. */ -static void flush_cpu_slab(void *d) +static void flush_cpu_slab(struct work_struct *w) { - struct kmem_cache *s = d; - struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab); + struct kmem_cache *s; + struct kmem_cache_cpu *c; + struct slub_flush_work *sfw; + + sfw = container_of(w, struct slub_flush_work, work); + + s = sfw->s; + c = this_cpu_ptr(s->cpu_slab); if (c->page) - flush_slab(s, c, false); + flush_slab(s, c, true); unfreeze_partials(s); } -static bool has_cpu_slab(int cpu, void *info) +static bool has_cpu_slab(int cpu, struct kmem_cache *s) { - struct kmem_cache *s = info; struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu); return c->page || slub_percpu_partial(c); } +static DEFINE_MUTEX(flush_lock); +static DEFINE_PER_CPU(struct slub_flush_work, slub_flush); + +static void flush_all_cpus_locked(struct kmem_cache *s) +{ + struct slub_flush_work *sfw; + unsigned int cpu; + + lockdep_assert_cpus_held(); + mutex_lock(&flush_lock); + + for_each_online_cpu(cpu) { + sfw = &per_cpu(slub_flush, cpu); + if (!has_cpu_slab(cpu, s)) { + sfw->skip = true; + continue; + } + INIT_WORK(&sfw->work, flush_cpu_slab); + sfw->skip = false; + sfw->s = s; + schedule_work_on(cpu, &sfw->work); + } + + for_each_online_cpu(cpu) { + sfw = &per_cpu(slub_flush, cpu); + if (sfw->skip) + continue; + flush_work(&sfw->work); + } + + mutex_unlock(&flush_lock); +} + static void flush_all(struct kmem_cache *s) { - on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1); + cpus_read_lock(); + flush_all_cpus_locked(s); + cpus_read_unlock(); } /* @@ -4087,7 +4133,7 @@ int __kmem_cache_shutdown(struct kmem_cache *s) int node; struct kmem_cache_node *n; - flush_all(s); + flush_all_cpus_locked(s); /* Attempt to free all objects */ for_each_kmem_cache_node(s, node, n) { free_partial(s, n); @@ -4363,7 +4409,7 @@ EXPORT_SYMBOL(kfree); * being allocated from last increasing the chance that the last objects * are freed in them. */ -int __kmem_cache_shrink(struct kmem_cache *s) +static int __kmem_cache_do_shrink(struct kmem_cache *s) { int node; int i; @@ -4375,7 +4421,6 @@ int __kmem_cache_shrink(struct kmem_cache *s) unsigned long flags; int ret = 0; - flush_all(s); for_each_kmem_cache_node(s, node, n) { INIT_LIST_HEAD(&discard); for (i = 0; i < SHRINK_PROMOTE_MAX; i++) @@ -4425,13 +4470,21 @@ int __kmem_cache_shrink(struct kmem_cache *s) return ret; } +int __kmem_cache_shrink(struct kmem_cache *s) +{ + flush_all(s); + return __kmem_cache_do_shrink(s); +} + static int slab_mem_going_offline_callback(void *arg) { struct kmem_cache *s; mutex_lock(&slab_mutex); - list_for_each_entry(s, &slab_caches, list) - __kmem_cache_shrink(s); + list_for_each_entry(s, &slab_caches, list) { + flush_all_cpus_locked(s); + __kmem_cache_do_shrink(s); + } mutex_unlock(&slab_mutex); return 0;