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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA587C433EF for ; Fri, 12 Nov 2021 03:02:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BA6560555 for ; Fri, 12 Nov 2021 03:02:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234545AbhKLDFk (ORCPT ); Thu, 11 Nov 2021 22:05:40 -0500 Received: from mga09.intel.com ([134.134.136.24]:22166 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233752AbhKLDFj (ORCPT ); Thu, 11 Nov 2021 22:05:39 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10165"; a="232907556" X-IronPort-AV: E=Sophos;i="5.87,227,1631602800"; d="scan'208";a="232907556" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Nov 2021 19:02:49 -0800 X-IronPort-AV: E=Sophos;i="5.87,227,1631602800"; d="scan'208";a="504707445" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.239.159.101]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Nov 2021 19:02:46 -0800 From: "Huang, Ying" To: Baolin Wang Cc: , , , , , , , , Subject: Re: [PATCH v3] mm: migrate: Support multiple target nodes demotion References: <87y25uks84.fsf@yhuang6-desk2.ccr.corp.intel.com> <8af6715f-c65b-b73b-f863-2c72ebc8544e@linux.alibaba.com> Date: Fri, 12 Nov 2021 11:02:44 +0800 In-Reply-To: <8af6715f-c65b-b73b-f863-2c72ebc8544e@linux.alibaba.com> (Baolin Wang's message of "Fri, 12 Nov 2021 10:58:42 +0800") Message-ID: <87tugikre3.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 Baolin Wang writes: > On 2021/11/12 10:44, Huang, Ying wrote: >> Baolin Wang writes: >> >>> We have some machines with multiple memory types like below, which >>> have one fast (DRAM) memory node and two slow (persistent memory) memory >>> nodes. According to current node demotion policy, if node 0 fills up, >>> its memory should be migrated to node 1, when node 1 fills up, its >>> memory will be migrated to node 2: node 0 -> node 1 -> node 2 ->stop. >>> >>> But this is not efficient and suitbale memory migration route >>> for our machine with multiple slow memory nodes. Since the distance >>> between node 0 to node 1 and node 0 to node 2 is equal, and memory >>> migration between slow memory nodes will increase persistent memory >>> bandwidth greatly, which will hurt the whole system's performance. >>> >>> Thus for this case, we can treat the slow memory node 1 and node 2 >>> as a whole slow memory region, and we should migrate memory from >>> node 0 to node 1 and node 2 if node 0 fills up. >>> >>> This patch changes the node_demotion data structure to support multiple >>> target nodes, and establishes the migration path to support multiple >>> target nodes with validating if the node distance is the best or not. >>> >>> available: 3 nodes (0-2) >>> node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 >>> node 0 size: 62153 MB >>> node 0 free: 55135 MB >>> node 1 cpus: >>> node 1 size: 127007 MB >>> node 1 free: 126930 MB >>> node 2 cpus: >>> node 2 size: 126968 MB >>> node 2 free: 126878 MB >>> node distances: >>> node 0 1 2 >>> 0: 10 20 20 >>> 1: 20 10 20 >>> 2: 20 20 10 >>> >>> Signed-off-by: Baolin Wang > > snip > >>> /* >>> * 'next_pass' contains nodes which became migration >>> @@ -3192,6 +3281,14 @@ static int __init migrate_on_reclaim_init(void) >>> { >>> int ret; >>> + /* >>> + * Ignore allocation failure, if this kmalloc fails >>> + * at boot time, we are likely in bigger trouble. >>> + */ >>> + node_demotion = kmalloc_array(nr_node_ids, >>> + sizeof(struct demotion_nodes), >>> + GFP_KERNEL); >>> + >> I think we should WARN_ON() here. > > In this unlikey case, I think the mm core will print more information, > IMHO WARN_ON() will help little. Anyway no strong opinion on > this. Other than that, can I get your reviewed-by tag with this nit > fixed? Thanks. Yes. Please add my "reviewed-by" after changing this. Best Regards, Huang, Ying