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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5800FC2D0CE for ; Wed, 22 Jan 2020 00:36:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 343732253D for ; Wed, 22 Jan 2020 00:36:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728913AbgAVAgl (ORCPT ); Tue, 21 Jan 2020 19:36:41 -0500 Received: from mga04.intel.com ([192.55.52.120]:19225 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726876AbgAVAgk (ORCPT ); Tue, 21 Jan 2020 19:36:40 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Jan 2020 16:36:40 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,347,1574150400"; d="scan'208";a="250443555" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga004.fm.intel.com with ESMTP; 21 Jan 2020 16:36:39 -0800 Date: Wed, 22 Jan 2020 08:36:50 +0800 From: Wei Yang To: Michal Hocko Cc: Wei Yang , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yang.shi@linux.alibaba.com Subject: Re: [PATCH 1/8] mm/migrate.c: skip node check if done in last round Message-ID: <20200122003650.GA11409@richard> Reply-To: Wei Yang References: <20200119030636.11899-1-richardw.yang@linux.intel.com> <20200119030636.11899-2-richardw.yang@linux.intel.com> <20200120093646.GL18451@dhcp22.suse.cz> <20200120222540.GA32314@richard> <20200121084205.GD29276@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200121084205.GD29276@dhcp22.suse.cz> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 21, 2020 at 09:42:05AM +0100, Michal Hocko wrote: >On Tue 21-01-20 06:25:40, Wei Yang wrote: >> On Mon, Jan 20, 2020 at 10:36:46AM +0100, Michal Hocko wrote: >> >On Sun 19-01-20 11:06:29, Wei Yang wrote: >> >> Before move page to target node, we would check if the node id is valid. >> >> In case we would try to move pages to the same target node, it is not >> >> necessary to do the check each time. >> >> >> >> This patch tries to skip the check if the node has been checked. >> >> >> >> Signed-off-by: Wei Yang >> >> --- >> >> mm/migrate.c | 19 +++++++++++-------- >> >> 1 file changed, 11 insertions(+), 8 deletions(-) >> >> >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> >> index 430fdccc733e..ba7cf4fa43a0 100644 >> >> --- a/mm/migrate.c >> >> +++ b/mm/migrate.c >> >> @@ -1612,15 +1612,18 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, >> >> goto out_flush; >> >> addr = (unsigned long)untagged_addr(p); >> >> >> >> - err = -ENODEV; >> >> - if (node < 0 || node >= MAX_NUMNODES) >> >> - goto out_flush; >> >> - if (!node_state(node, N_MEMORY)) >> >> - goto out_flush; >> >> + /* Check node if it is not checked. */ >> >> + if (current_node == NUMA_NO_NODE || node != current_node) { >> >> + err = -ENODEV; >> >> + if (node < 0 || node >= MAX_NUMNODES) >> >> + goto out_flush; >> >> + if (!node_state(node, N_MEMORY)) >> >> + goto out_flush; >> > >> >This makes the code harder to read IMHO. The original code checks the >> >valid node first and it doesn't conflate that with the node caching >> >logic which your change does. >> > >> >> I am sorry, would you mind showing me an example about the conflate in my >> change? I don't get it. > >NUMA_NO_NODE is the iteration logic, right? It resets the batching node. >Node check read from the userspace is an input sanitization. Do not put >those two into the same checks. More clear now? Yes, I see your point. Can we think like this: On each iteration, we do an input sanitization? Well, this is a trivial one. If you don't like it, I would remove this. >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me