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 27B60C433F5 for ; Thu, 11 Nov 2021 00:44:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00DD66128E for ; Thu, 11 Nov 2021 00:44:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231895AbhKKArQ (ORCPT ); Wed, 10 Nov 2021 19:47:16 -0500 Received: from mga14.intel.com ([192.55.52.115]:48590 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230312AbhKKArO (ORCPT ); Wed, 10 Nov 2021 19:47:14 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10164"; a="233067069" X-IronPort-AV: E=Sophos;i="5.87,225,1631602800"; d="scan'208";a="233067069" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Nov 2021 16:44:25 -0800 X-IronPort-AV: E=Sophos;i="5.87,225,1631602800"; d="scan'208";a="504211898" 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; 10 Nov 2021 16:44:22 -0800 From: "Huang, Ying" To: Baolin Wang Cc: , , , , , , , , Subject: Re: [PATCH] mm: migrate: Support multiple target nodes demotion References: <8850612186ea23eb5d328d84e4008a6b60f418e1.1636514506.git.baolin.wang@linux.alibaba.com> <87ee7opf4p.fsf@yhuang6-desk2.ccr.corp.intel.com> Date: Thu, 11 Nov 2021 08:44:20 +0800 In-Reply-To: (Baolin Wang's message of "Wed, 10 Nov 2021 18:45:17 +0800") Message-ID: <87a6ibplln.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 2021/11/10 16:51, Huang, Ying writes: >> 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, if node 0 fills up, >> ~~~~~~~~~~~~~ >> node demotion policy? > > Yes, will fix in next version. > >> >>> 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 >>> --- >>> Changes from RFC v2: >>> - Change to 'short' type for target nodes array. >>> - Remove nodemask instead selecting target node directly. >>> - Add WARN_ONCE() if the target nodes exceed the maximum value. >>> >>> Changes from RFC v1: >>> - Re-define the node_demotion structure. >>> - Set up multiple target nodes by validating the node distance. >>> - Add more comments. >>> --- >>> mm/migrate.c | 138 +++++++++++++++++++++++++++++++++++++++++++---------------- >>> 1 file changed, 102 insertions(+), 36 deletions(-) >>> >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index cf25b00..7f1d745 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -50,6 +50,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> #include >>> @@ -1119,12 +1120,25 @@ static int __unmap_and_move(struct page >>> *page, struct page *newpage, >>> * >>> * This is represented in the node_demotion[] like this: >>> * >>> - * { 1, // Node 0 migrates to 1 >>> - * 2, // Node 1 migrates to 2 >>> - * -1, // Node 2 does not migrate >>> - * 4, // Node 3 migrates to 4 >>> - * 5, // Node 4 migrates to 5 >>> - * -1} // Node 5 does not migrate >>> + * { nr=1, nodes[0]=1 }, // Node 0 migrates to 1 >>> + * { nr=1, nodes[0]=2 }, // Node 1 migrates to 2 >>> + * { nr=0, nodes[0]=-1 }, // Node 2 does not migrate >>> + * { nr=1, nodes[0]=4 }, // Node 3 migrates to 4 >>> + * { nr=1, nodes[0]=5 }, // Node 4 migrates to 5 >>> + * { nr=0, nodes[0]=-1} // Node 5 does not migrate >>> + * >>> + * Moreover some systems may have multiple same class memory >>> + * types. Suppose a system has one socket with 3 memory nodes, >> s/same class memory types/slow memory nodes/ >> ? >> We don't support multiple fast memory types, right? > > Until now we have no machines with multiple fast memory types. OK, I > will change the words. > >> >>> + * node 0 is fast memory type, and node 1/2 both are slow memory >>> + * type, and the distance between fast memory node and slow >>> + * memory node is same. So the migration path should be: >>> + * >>> + * 0 -> 1/2 -> stop >>> + * >>> + * This is represented in the node_demotion[] like this: >>> + * { nr=2, {nodes[0]=1, nodes[1]=2} }, // Node 0 migrates to node 1 and node 2 >>> + * { nr=0, nodes[0]=-1, }, // Node 1 dose not migrate >>> + * { nr=0, nodes[0]=-1, }, // Node 2 does not migrate >>> */ >>> /* >>> @@ -1135,8 +1149,13 @@ static int __unmap_and_move(struct page *page, struct page *newpage, >>> * must be held over all reads to ensure that no cycles are >>> * observed. >>> */ >>> -static int node_demotion[MAX_NUMNODES] __read_mostly = >>> - {[0 ... MAX_NUMNODES - 1] = NUMA_NO_NODE}; >>> +#define DEMOTION_TARGET_NODES 15 >>> +struct demotion_nodes { >>> + unsigned short nr; >>> + short nodes[DEMOTION_TARGET_NODES]; >>> +}; >>> + >>> +static struct demotion_nodes node_demotion[MAX_NUMNODES] __read_mostly; >> If MAX_NUMNODES is 1024, the total size will be (16 * 2 * 1024) = >> 32K >> bytes. That appears too large. We may consider to allocate >> node_demotion[] dynamically. > > Sure. I'd like to optimize it in a separate patch to keep current > patch easy to review. Thanks. OK. And we can keep DEMOTION_TARGET_NODES < MAX_NUMNODES. Best Regards, Huang, Ying