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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05ADAC433F5 for ; Fri, 11 Mar 2022 05:06:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242853AbiCKFHf (ORCPT ); Fri, 11 Mar 2022 00:07:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233316AbiCKFHd (ORCPT ); Fri, 11 Mar 2022 00:07:33 -0500 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58CE61AC28A for ; Thu, 10 Mar 2022 21:06:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646975191; x=1678511191; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=OOgJlZoe9IV6UW0OwCBHgfvN99zJHLrs7RVdXfzZ7TU=; b=bHM+0rqvaAnrcDXIiVWcQTWVFmV3LRKYvaPbgNoej3q4mOxphgUYxk1p xX8ULei+dbFizC5xBI2VwrF3PnFuncqHtrRpwGaMfp+bQf1XdcPa/rMf+ wSYRLU9xD/hsvx0ruggR+wkGzwaGuNSS3rJ3jVqAMJE1kxJwAaWwv0PM+ EnBu0Ua1v7ngVmX+OdJJe2KDypQugC7MCXNKVVP3kD+yWneKZVavuLM8j mciHa4TKYvroVzP1E54VV12tVfdPRBy5bnYxoKItXUXnNiglSJqBUBeLq 6rx00SRZoTNzBlRFORaBxhJ+2o3mVXu0LoVAeQNKrtBnQm4VAQLRweEie w==; X-IronPort-AV: E=McAfee;i="6200,9189,10282"; a="316221579" X-IronPort-AV: E=Sophos;i="5.90,172,1643702400"; d="scan'208";a="316221579" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2022 21:06:30 -0800 X-IronPort-AV: E=Sophos;i="5.90,172,1643702400"; d="scan'208";a="642870004" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.239.13.94]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2022 21:06:28 -0800 From: "Huang, Ying" To: Oscar Salvador Cc: Andrew Morton , Dave Hansen , Abhishek Goel , Baolin Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm: Only re-generate demotion targets when a numa node changes its N_CPU state References: <20220310120749.23077-1-osalvador@suse.de> Date: Fri, 11 Mar 2022 13:06:26 +0800 In-Reply-To: <20220310120749.23077-1-osalvador@suse.de> (Oscar Salvador's message of "Thu, 10 Mar 2022 13:07:49 +0100") Message-ID: <87a6dxaxil.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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > v1 -> v2: - Fix prototype function declaration > - Fix build error on RISC > - Adressed feedback from Baolin and Huang > --- > include/linux/migrate.h | 8 ++++++++ > mm/migrate.c | 41 +++++------------------------------------ > mm/vmstat.c | 13 ++++++++++++- > 3 files changed, 25 insertions(+), 37 deletions(-) > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index db96e10eb8da..90e75d5a54d6 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -48,7 +48,15 @@ int folio_migrate_mapping(struct address_space *mapping, > struct folio *newfolio, struct folio *folio, int extra_count); > > extern bool numa_demotion_enabled; > +extern void migrate_on_reclaim_init(void); > +#ifdef CONFIG_HOTPLUG_CPU > +extern void set_migration_target_nodes(void); > #else > +static inline void set_migration_target_nodes(void) {} > +#endif > +#else > + > +static inline void set_migration_target_nodes(void) {} > > static inline void putback_movable_pages(struct list_head *l) {} > static inline int migrate_pages(struct list_head *l, new_page_t new, > diff --git a/mm/migrate.c b/mm/migrate.c > index c7da064b4781..f9d5b6092a42 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(); > @@ -3254,51 +3254,20 @@ 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) > +void __init migrate_on_reclaim_init(void) > { > - 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. > + * At this point, all numa nodes with memory/CPus have their state > + * properly set, so we can build the demotion order now. > */ > - WARN_ON(ret < 0); > - ret = cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online", > - migration_online_cpu, NULL); > - WARN_ON(ret < 0); > - > + set_migration_target_nodes(); If my understanding were correct, we should enclose set_migration_target_nodes() here with cpus_read_lock(). And add some comment before set_migration_target_nodes() for this. I don't know whether the locking order is right. > hotplug_memory_notifier(migrate_on_reclaim_callback, 100); And we should register the notifier before calling set_migration_target_nodes()? Best Regards, Huang, Ying > - return 0; > } > -late_initcall(migrate_on_reclaim_init); > #endif /* CONFIG_HOTPLUG_CPU */ > [snip]