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 F1223C433EF for ; Fri, 11 Mar 2022 01:32:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 16A738D0002; Thu, 10 Mar 2022 20:32:42 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 11A238D0001; Thu, 10 Mar 2022 20:32:42 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F23D28D0002; Thu, 10 Mar 2022 20:32:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0027.hostedemail.com [216.40.44.27]) by kanga.kvack.org (Postfix) with ESMTP id DFFF28D0001 for ; Thu, 10 Mar 2022 20:32:41 -0500 (EST) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 96C219EB12 for ; Fri, 11 Mar 2022 01:32:41 +0000 (UTC) X-FDA: 79230380922.18.9C5FFD1 Received: from out30-42.freemail.mail.aliyun.com (out30-42.freemail.mail.aliyun.com [115.124.30.42]) by imf14.hostedemail.com (Postfix) with ESMTP id 1767B100008 for ; Fri, 11 Mar 2022 01:32:39 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0V6qnh1P_1646962355; Received: from 30.97.48.70(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0V6qnh1P_1646962355) by smtp.aliyun-inc.com(127.0.0.1); Fri, 11 Mar 2022 09:32:35 +0800 Message-ID: Date: Fri, 11 Mar 2022 09:33:39 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.2 Subject: Re: [PATCH v2] mm: Only re-generate demotion targets when a numa node changes its N_CPU state To: Oscar Salvador , Andrew Morton Cc: Dave Hansen , "Huang, Ying" , Abhishek Goel , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220310120749.23077-1-osalvador@suse.de> From: Baolin Wang In-Reply-To: <20220310120749.23077-1-osalvador@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1767B100008 X-Stat-Signature: y3xuxkxi5t7zgp4febsbxyoawcx1zzg6 Authentication-Results: imf14.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf14.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.42 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1646962359-247769 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: On 3/10/2022 8:07 PM, Oscar Salvador wrote: > 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(); > hotplug_memory_notifier(migrate_on_reclaim_callback, 100); > - return 0; > } > -late_initcall(migrate_on_reclaim_init); > #endif /* CONFIG_HOTPLUG_CPU */ > > bool numa_demotion_enabled = false; > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 4057372745d0..9e9536df51b5 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; > } > > @@ -2097,6 +2105,9 @@ void __init init_mm_internals(void) > > start_shepherd_timer(); > #endif > +#if defined(CONFIG_MIGRATION) && defined(CONFIG_HOTPLUG_CPU) > + migrate_on_reclaim_init(); I guess can we move these CONFIG_* macros into migrate.h like what set_migration_target_nodes() does? Otherwise LGTM. Please feel free to add: Reviewed-by: Baolin Wang Tested-by: Baolin Wang