From patchwork Wed Apr 20 09:59:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mel Gorman X-Patchwork-Id: 12820013 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 257D1C433F5 for ; Wed, 20 Apr 2022 10:00:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ACADE6B0088; Wed, 20 Apr 2022 06:00:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A79846B0087; Wed, 20 Apr 2022 06:00:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 91A846B0088; Wed, 20 Apr 2022 06:00:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 842036B0085 for ; Wed, 20 Apr 2022 06:00:23 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 5C82A824DA for ; Wed, 20 Apr 2022 10:00:23 +0000 (UTC) X-FDA: 79376812326.01.1FD174C Received: from outbound-smtp21.blacknight.com (outbound-smtp21.blacknight.com [81.17.249.41]) by imf19.hostedemail.com (Postfix) with ESMTP id 176BB1A0018 for ; Wed, 20 Apr 2022 10:00:20 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail04.blacknight.ie [81.17.254.17]) by outbound-smtp21.blacknight.com (Postfix) with ESMTPS id 920D9CCD6D for ; Wed, 20 Apr 2022 11:00:21 +0100 (IST) Received: (qmail 14142 invoked from network); 20 Apr 2022 10:00:21 -0000 Received: from unknown (HELO morpheus.112glenside.lan) (mgorman@techsingularity.net@[84.203.198.246]) by 81.17.254.9 with ESMTPA; 20 Apr 2022 10:00:21 -0000 From: Mel Gorman To: Nicolas Saenz Julienne Cc: Marcelo Tosatti , Vlastimil Babka , Michal Hocko , LKML , Linux-MM , Mel Gorman Subject: [PATCH 6/6] mm/page_alloc: Remotely drain per-cpu lists Date: Wed, 20 Apr 2022 10:59:06 +0100 Message-Id: <20220420095906.27349-7-mgorman@techsingularity.net> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220420095906.27349-1-mgorman@techsingularity.net> References: <20220420095906.27349-1-mgorman@techsingularity.net> MIME-Version: 1.0 Authentication-Results: imf19.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf19.hostedemail.com: domain of mgorman@techsingularity.net designates 81.17.249.41 as permitted sender) smtp.mailfrom=mgorman@techsingularity.net X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 176BB1A0018 X-Stat-Signature: uiyxzpwn5g14kiamnhf3k5zxqike7sti X-HE-Tag: 1650448820-413921 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: Nicolas Saenz Julienne Some setups, notably NOHZ_FULL CPUs, are too busy to handle the per-cpu drain work queued by __drain_all_pages(). So introduce new a mechanism to remotely drain the per-cpu lists. It is made possible by remotely locking 'struct per_cpu_pages' new per-cpu spinlocks. A benefit of this new scheme is that drain operations are now migration safe. There was no observed performance degradation vs. the previous scheme. Both netperf and hackbench were run in parallel to triggering the __drain_all_pages(NULL, true) code path around ~100 times per second. The new scheme performs a bit better (~5%), although the important point here is there are no performance regressions vs. the previous mechanism. Per-cpu lists draining happens only in slow paths. Link: https://lore.kernel.org/r/20211103170512.2745765-4-nsaenzju@redhat.com Signed-off-by: Nicolas Saenz Julienne Signed-off-by: Mel Gorman --- mm/page_alloc.c | 66 +++++++++---------------------------------------- 1 file changed, 11 insertions(+), 55 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 813c84b67c65..17d11eb0413e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -161,13 +161,7 @@ DEFINE_PER_CPU(int, _numa_mem_); /* Kernel "local memory" node */ EXPORT_PER_CPU_SYMBOL(_numa_mem_); #endif -/* work_structs for global per-cpu drains */ -struct pcpu_drain { - struct zone *zone; - struct work_struct work; -}; static DEFINE_MUTEX(pcpu_drain_mutex); -static DEFINE_PER_CPU(struct pcpu_drain, pcpu_drain); #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY volatile unsigned long latent_entropy __latent_entropy; @@ -3087,9 +3081,6 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, * Called from the vmstat counter updater to drain pagesets of this * currently executing processor on remote nodes after they have * expired. - * - * Note that this function must be called with the thread pinned to - * a single processor. */ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp) { @@ -3114,10 +3105,6 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp) /* * Drain pcplists of the indicated processor and zone. - * - * The processor must either be the current processor and the - * thread pinned to the current processor or a processor that - * is not online. */ static void drain_pages_zone(unsigned int cpu, struct zone *zone) { @@ -3140,10 +3127,6 @@ static void drain_pages_zone(unsigned int cpu, struct zone *zone) /* * Drain pcplists of all zones on the indicated processor. - * - * The processor must either be the current processor and the - * thread pinned to the current processor or a processor that - * is not online. */ static void drain_pages(unsigned int cpu) { @@ -3156,9 +3139,6 @@ static void drain_pages(unsigned int cpu) /* * Spill all of this CPU's per-cpu pages back into the buddy allocator. - * - * The CPU has to be pinned. When zone parameter is non-NULL, spill just - * the single zone's pages. */ void drain_local_pages(struct zone *zone) { @@ -3170,24 +3150,6 @@ void drain_local_pages(struct zone *zone) drain_pages(cpu); } -static void drain_local_pages_wq(struct work_struct *work) -{ - struct pcpu_drain *drain; - - drain = container_of(work, struct pcpu_drain, work); - - /* - * drain_all_pages doesn't use proper cpu hotplug protection so - * we can race with cpu offline when the WQ can move this from - * a cpu pinned worker to an unbound one. We can operate on a different - * cpu which is alright but we also have to make sure to not move to - * a different one. - */ - migrate_disable(); - drain_local_pages(drain->zone); - migrate_enable(); -} - /* * The implementation of drain_all_pages(), exposing an extra parameter to * drain on all cpus. @@ -3208,13 +3170,6 @@ static void __drain_all_pages(struct zone *zone, bool force_all_cpus) */ static cpumask_t cpus_with_pcps; - /* - * Make sure nobody triggers this path before mm_percpu_wq is fully - * initialized. - */ - if (WARN_ON_ONCE(!mm_percpu_wq)) - return; - /* * Do not drain if one is already in progress unless it's specific to * a zone. Such callers are primarily CMA and memory hotplug and need @@ -3264,14 +3219,12 @@ static void __drain_all_pages(struct zone *zone, bool force_all_cpus) } for_each_cpu(cpu, &cpus_with_pcps) { - struct pcpu_drain *drain = per_cpu_ptr(&pcpu_drain, cpu); - - drain->zone = zone; - INIT_WORK(&drain->work, drain_local_pages_wq); - queue_work_on(cpu, mm_percpu_wq, &drain->work); + if (zone) { + drain_pages_zone(cpu, zone); + } else { + drain_pages(cpu); + } } - for_each_cpu(cpu, &cpus_with_pcps) - flush_work(&per_cpu_ptr(&pcpu_drain, cpu)->work); mutex_unlock(&pcpu_drain_mutex); } @@ -3280,8 +3233,6 @@ static void __drain_all_pages(struct zone *zone, bool force_all_cpus) * Spill all the per-cpu pages from all CPUs back into the buddy allocator. * * When zone parameter is non-NULL, spill just the single zone's pages. - * - * Note that this can be extremely slow as the draining happens in a workqueue. */ void drain_all_pages(struct zone *zone) { @@ -3559,7 +3510,12 @@ void free_unref_page_list(struct list_head *list) trace_mm_page_free_batched(page); - /* True is dead code at the moment due to local_lock_irqsave. */ + /* + * If there is a parallel drain in progress, free to the buddy + * allocator directly. This is expensive as the zone lock will + * be acquired multiple times but if a drain is in progress + * then an expensive operation is already taking place. + */ if (unlikely(!free_unref_page_commit(page, migratetype, 0, true))) free_one_page(page_zone(page), page, page_to_pfn(page), 0, migratetype, FPI_NONE);