From patchwork Fri Jun 24 12:54:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mel Gorman X-Patchwork-Id: 12894472 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 2E76FC433EF for ; Fri, 24 Jun 2022 12:55:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B62FA8E021C; Fri, 24 Jun 2022 08:55:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AEAE68E020E; Fri, 24 Jun 2022 08:55:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 965238E021C; Fri, 24 Jun 2022 08:55:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 80C9C8E020E for ; Fri, 24 Jun 2022 08:55:40 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 3F25135C for ; Fri, 24 Jun 2022 12:55:40 +0000 (UTC) X-FDA: 79613126040.21.6FA75AB Received: from outbound-smtp59.blacknight.com (outbound-smtp59.blacknight.com [46.22.136.243]) by imf13.hostedemail.com (Postfix) with ESMTP id 819BC200BF for ; Fri, 24 Jun 2022 12:55:39 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp59.blacknight.com (Postfix) with ESMTPS id 4A2B0FAC58 for ; Fri, 24 Jun 2022 13:55:38 +0100 (IST) Received: (qmail 9039 invoked from network); 24 Jun 2022 12:55:38 -0000 Received: from unknown (HELO morpheus.112glenside.lan) (mgorman@techsingularity.net@[84.203.198.246]) by 81.17.254.9 with ESMTPA; 24 Jun 2022 12:55:37 -0000 From: Mel Gorman To: Andrew Morton Cc: Nicolas Saenz Julienne , Marcelo Tosatti , Vlastimil Babka , Michal Hocko , Hugh Dickins , Yu Zhao , Marek Szyprowski , LKML , Linux-MM , Mel Gorman Subject: [PATCH 6/7] mm/page_alloc: Remotely drain per-cpu lists Date: Fri, 24 Jun 2022 13:54:22 +0100 Message-Id: <20220624125423.6126-7-mgorman@techsingularity.net> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220624125423.6126-1-mgorman@techsingularity.net> References: <20220624125423.6126-1-mgorman@techsingularity.net> MIME-Version: 1.0 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656075339; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QpA8dZbBS3S9+tI0/MYI/sjCM2nrohd0Oe8cEsuEQY4=; b=3wGODeV39sLbuKh0ShSiddkggNPY/hkf/7C7MisEKdmnQzSLHo/YpTDswy437HuvV2sglQ 4eDGu4sVPwfh3+YLz6wFe0lIaXg7Jv7pQ+ZHFJkYV08lZEjJJIqRwU21PbjbrBseljtHyH kyntl/QYVS7oxghnVtSPYEo+OEgvUQU= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=none; spf=pass (imf13.hostedemail.com: domain of mgorman@techsingularity.net designates 46.22.136.243 as permitted sender) smtp.mailfrom=mgorman@techsingularity.net; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656075339; a=rsa-sha256; cv=none; b=mESM8mRAm1WoXzpman6YswnZgwjJzRJQyoyN31VzHo+AXeFc2gAWbSs2+PwcVhnc+Qnv8s pnHg1ZdnGR1YeoWm9rS0FHVIS2kY6fBQnV4FAFprcelAd62zK7H9EmkAkeZtZXovPlKldr N6WepjOwx1P6XLREHeObjr7VF+QaKm8= Authentication-Results: imf13.hostedemail.com; dkim=none; spf=pass (imf13.hostedemail.com: domain of mgorman@techsingularity.net designates 46.22.136.243 as permitted sender) smtp.mailfrom=mgorman@techsingularity.net; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: bakpod4nocc5rmqn9nj4a1r771fqfjnt X-Rspamd-Queue-Id: 819BC200BF X-HE-Tag: 1656075339-551153 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 a new 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. Minchan Kim tested an earlier version and reported; My workload is not NOHZ CPUs but run apps under heavy memory pressure so they goes to direct reclaim and be stuck on drain_all_pages until work on workqueue run. unit: nanosecond max(dur) avg(dur) count(dur) 166713013 487511.77786438033 1283 From traces, system encountered the drain_all_pages 1283 times and worst case was 166ms and avg was 487us. The other problem was alloc_contig_range in CMA. The PCP draining takes several hundred millisecond sometimes though there is no memory pressure or a few of pages to be migrated out but CPU were fully booked. Your patch perfectly removed those wasted time. Signed-off-by: Nicolas Saenz Julienne Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka --- mm/page_alloc.c | 58 ++++--------------------------------------------- 1 file changed, 4 insertions(+), 54 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3b819c2720f8..44e7c29aaa7d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -165,13 +165,7 @@ 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; @@ -3105,9 +3099,6 @@ 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) { @@ -3132,10 +3123,6 @@ 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) { @@ -3154,10 +3141,6 @@ 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) { @@ -3170,9 +3153,6 @@ 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) { @@ -3184,24 +3164,6 @@ 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. @@ -3222,13 +3184,6 @@ 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 @@ -3278,14 +3233,11 @@ 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); } @@ -3294,8 +3246,6 @@ 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) {