From mboxrd@z Thu Jan 1 00:00:00 1970 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 0AB56C433FE for ; Thu, 10 Mar 2022 00:40:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7158D8D0002; Wed, 9 Mar 2022 19:40:01 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 69CDF8D0001; Wed, 9 Mar 2022 19:40:01 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 516CC8D0002; Wed, 9 Mar 2022 19:40:01 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0042.hostedemail.com [216.40.44.42]) by kanga.kvack.org (Postfix) with ESMTP id 3E3238D0001 for ; Wed, 9 Mar 2022 19:40:01 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id EBA2D181C1927 for ; Thu, 10 Mar 2022 00:40:00 +0000 (UTC) X-FDA: 79226619360.24.B90FD64 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf16.hostedemail.com (Postfix) with ESMTP id A113318000C for ; Thu, 10 Mar 2022 00:39:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646872799; x=1678408799; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=X2z+zSN/i5yI6VGeE+HYqJx2M+Kg5IqbBL0UPebJfPU=; b=MPaC+aATMoUIQxEGJ/Kog1aq+pjw7PAwm1550Nf68tGqIc7NvTzeJFIf 54cpG20ETtaoAQS7Zdvjmev6lS0T7TqH+hRhmlVAjdMvzvxhTtvgyFjjV 0mZ3j4z7/9PFbUReAhOkwKYZFYs+EyvUp4vhmEMr837OcsAh2d4G7A8mz c1s4bGBOjr90Hc2lEr4fEIDtP65Ibgmd+eDKgCNuHdPm6or9pPEC3bZzr S7Ph5WhLo03oACDReSgBmR/8v5x+s9+oA9PyeZDmBzzpVnfV0e/pzTCc8 TE+J/13BxK+AAEIoyDXnM0wn+pNtg7M6sczpR7CnD8vEcKpsSd8ZhC8c1 g==; X-IronPort-AV: E=McAfee;i="6200,9189,10281"; a="318348485" X-IronPort-AV: E=Sophos;i="5.90,169,1643702400"; d="scan'208";a="318348485" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Mar 2022 16:39:57 -0800 X-IronPort-AV: E=Sophos;i="5.90,169,1643702400"; d="scan'208";a="513758433" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.239.13.94]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Mar 2022 16:39:55 -0800 From: "Huang, Ying" To: Oscar Salvador Cc: Andrew Morton , Dave Hansen , Abhishek Goel , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Only re-generate demotion targets when a numa node changes its N_CPU state References: <20220309144644.4278-1-osalvador@suse.de> Date: Thu, 10 Mar 2022 08:39:53 +0800 In-Reply-To: <20220309144644.4278-1-osalvador@suse.de> (Oscar Salvador's message of "Wed, 9 Mar 2022 15:46:44 +0100") Message-ID: <87bkyefxnq.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A113318000C X-Stat-Signature: tadsb94okyyaco9kaz7dws6y4dx6qscr Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=MPaC+aAT; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf16.hostedemail.com: domain of ying.huang@intel.com has no SPF policy when checking 134.134.136.100) smtp.mailfrom=ying.huang@intel.com X-HE-Tag: 1646872799-650477 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: Oscar Salvador writes: > Abhishek reported that after patch [1], hotplug operations are > taking ~double the expected time. [2] > > The reason behind is that the CPU callbacks that migrate_on_reclaim_init() > sets always call set_migration_target_nodes() whenever a CPU is brought > up/down. > But we only care about numa nodes going from having cpus to become > cpuless, and vice versa, as that influences the demotion_target order. > > We do already have two CPU callbacks (vmstat_cpu_online() and vmstat_cpu_dead()) > that check exactly that, so get rid of the CPU callbacks in > migrate_on_reclaim_init() and only call set_migration_target_nodes() from > vmstat_cpu_{dead,online}() whenever a numa node change its N_CPU state. > > [1] https://lore.kernel.org/linux-mm/20210721063926.3024591-2-ying.huang@intel.com/ > [2] https://lore.kernel.org/linux-mm/eb438ddd-2919-73d4-bd9f-b7eecdd9577a@linux.vnet.ibm.com/ > > Reported-by: Abhishek Goel > Signed-off-by: Oscar Salvador > --- > I think there is further room for improvement like should we call in to > set_migration_target_nodes() when demotion is disabled via sysctl? > I will have a look into that, but let us go with this quick fix for now. > Also, I am not really strong about the Fixes tag, but it can be added > if you think it makes sense. > --- > include/linux/migrate.h | 5 +++++ > mm/migrate.c | 36 +----------------------------------- > mm/vmstat.c | 10 +++++++++- > 3 files changed, 15 insertions(+), 36 deletions(-) > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index db96e10eb8da..c64fe2923fb0 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -48,6 +48,11 @@ int folio_migrate_mapping(struct address_space *mapping, > struct folio *newfolio, struct folio *folio, int extra_count); > > extern bool numa_demotion_enabled; > +#ifdef CONFIG_HOTPLUG_CPU > +extern void set_migration_target_nodes(void); > +#else > +static inline void set_migration_target_nodes() {} > +#endif > #else > > static inline void putback_movable_pages(struct list_head *l) {} > diff --git a/mm/migrate.c b/mm/migrate.c > index c7da064b4781..7847e4de01d7 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -3190,7 +3190,7 @@ static void __set_migration_target_nodes(void) > /* > * For callers that do not hold get_online_mems() already. > */ > -static void set_migration_target_nodes(void) > +void set_migration_target_nodes(void) > { > get_online_mems(); > __set_migration_target_nodes(); > @@ -3254,47 +3254,13 @@ static int __meminit migrate_on_reclaim_callback(struct notifier_block *self, > return notifier_from_errno(0); > } > > -/* > - * React to hotplug events that might affect the migration targets > - * like events that online or offline NUMA nodes. > - * > - * The ordering is also currently dependent on which nodes have > - * CPUs. That means we need CPU on/offline notification too. > - */ > -static int migration_online_cpu(unsigned int cpu) > -{ > - set_migration_target_nodes(); > - return 0; > -} > - > -static int migration_offline_cpu(unsigned int cpu) > -{ > - set_migration_target_nodes(); > - return 0; > -} > - > static int __init migrate_on_reclaim_init(void) > { > - int ret; > - > node_demotion = kmalloc_array(nr_node_ids, > sizeof(struct demotion_nodes), > GFP_KERNEL); > WARN_ON(!node_demotion); > > - ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD, "mm/demotion:offline", > - NULL, migration_offline_cpu); > - /* > - * In the unlikely case that this fails, the automatic > - * migration targets may become suboptimal for nodes > - * where N_CPU changes. With such a small impact in a > - * rare case, do not bother trying to do anything special. > - */ > - WARN_ON(ret < 0); > - ret = cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online", > - migration_online_cpu, NULL); > - WARN_ON(ret < 0); > - We need to call set_migration_target_nodes() during system boot somewhere, either here or in init_mm_internals(). Best Regards, Huang, Ying > hotplug_memory_notifier(migrate_on_reclaim_callback, 100); > return 0; > } > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 4057372745d0..0529a83c8f89 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -28,6 +28,7 @@ > #include > #include > #include > +#include > > #include "internal.h" > > @@ -2043,7 +2044,12 @@ static void __init init_cpu_node_state(void) > static int vmstat_cpu_online(unsigned int cpu) > { > refresh_zone_stat_thresholds(); > - node_set_state(cpu_to_node(cpu), N_CPU); > + > + if (!node_state(cpu_to_node(cpu), N_CPU)) { > + node_set_state(cpu_to_node(cpu), N_CPU); > + set_migration_target_nodes(); > + } > + > return 0; > } > > @@ -2066,6 +2072,8 @@ static int vmstat_cpu_dead(unsigned int cpu) > return 0; > > node_clear_state(node, N_CPU); > + set_migration_target_nodes(); > + > return 0; > }