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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 12052C4742C for ; Wed, 11 Nov 2020 06:50:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA5BF20786 for ; Wed, 11 Nov 2020 06:50:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725995AbgKKGuN (ORCPT ); Wed, 11 Nov 2020 01:50:13 -0500 Received: from mga05.intel.com ([192.55.52.43]:30347 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725882AbgKKGuM (ORCPT ); Wed, 11 Nov 2020 01:50:12 -0500 IronPort-SDR: KF0kMh6MvV/Md5RoC3pfXIrWibP9RRrt5HZHBjWqyjsbeI7ACdvYfKXpS3IOzCd2TQ4XntkR03 uo69grgpLcnw== X-IronPort-AV: E=McAfee;i="6000,8403,9801"; a="254813109" X-IronPort-AV: E=Sophos;i="5.77,468,1596524400"; d="scan'208";a="254813109" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Nov 2020 22:50:12 -0800 IronPort-SDR: Ps/7aR3q9CySFdV9ZwR7dKqpPUUIQ+PSDQcFNh7FTPkKcC+/I8PVN5oOidodpGLwNpkHP4vDS7 0RYDH8C8QAQA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,468,1596524400"; d="scan'208";a="338984011" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.120]) by orsmga002.jf.intel.com with ESMTP; 10 Nov 2020 22:50:08 -0800 From: "Huang\, Ying" To: Mel Gorman Cc: Peter Zijlstra , , , Andrew Morton , Ingo Molnar , Rik van Riel , "Johannes Weiner" , "Matthew Wilcox \(Oracle\)" , Dave Hansen , Andi Kleen , Michal Hocko , David Rientjes Subject: Re: [PATCH -V2 2/2] autonuma: Migrate on fault among multiple bound nodes References: <20201028023411.15045-1-ying.huang@intel.com> <20201028023411.15045-3-ying.huang@intel.com> <20201102111717.GB3306@suse.de> <87eel9wumd.fsf@yhuang-dev.intel.com> <20201105112523.GQ3306@suse.de> Date: Wed, 11 Nov 2020 14:50:07 +0800 In-Reply-To: <20201105112523.GQ3306@suse.de> (Mel Gorman's message of "Thu, 5 Nov 2020 11:25:23 +0000") Message-ID: <87blg48k0w.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Mel, Mel Gorman writes: > On Wed, Nov 04, 2020 at 01:36:58PM +0800, Huang, Ying wrote: >> > I've no specific objection to the patch or the name change. I can't >> > remember exactly why I picked the name, it was 8 years ago but I think it >> > was because the policy represented the most basic possible approach that >> > could be done without any attempt at being intelligent and established >> > a baseline. The intent was that anything built on top had to be better >> > than the most basic policy imaginable. The name reflected the dictionary >> > definition at the time and happened to match the acronym closely enough >> > and I wanted to make it absolutely clear to reviewers that the policy >> > was not good enough (ruling out MPOL_BASIC or variants thereof) even if >> > it happened to work for some workload and there was no intent to report >> > it to the userspace API. >> > >> > The only hazard with the patch is that applications that use MPOL_BIND >> > on multiple nodes may now incur some NUMA balancing overhead due to >> > trapping faults and migrations. >> >> For this specific version of patch, I don't think this will happen. >> Because now, MPOL_F_MOF need to be set in struct mempolicy, for >> MPOL_BIND, only if mbind() syscall is called with MPOL_MF_LAZY, that >> will be the case. So I think most workloads will not be affected by >> this patch. The feature is opt-in. >> > > Ok. I just found MPOL_MF_LAZY is disabled now. And as in commit a720094ded8c ("mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now"), the ABI needs to be revisted before exporting to the user space formally. Sorry about that, I should have found that earlier. Think about that. I think MPOL_MF_LAZY is tied with MPOL_MF_MOVE, so it's semantics isn't good for the purpose of the patch. So I have rewritten the patch and the description and sent it as follows, can you help to review it? https://lore.kernel.org/lkml/20201111063717.186589-1-ying.huang@intel.com/ Best Regards, Huang, Ying