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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 3F305C432BE for ; Fri, 30 Jul 2021 07:18:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 25D5E61008 for ; Fri, 30 Jul 2021 07:18:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237869AbhG3HSw (ORCPT ); Fri, 30 Jul 2021 03:18:52 -0400 Received: from mga07.intel.com ([134.134.136.100]:32138 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237639AbhG3HSu (ORCPT ); Fri, 30 Jul 2021 03:18:50 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10060"; a="276823009" X-IronPort-AV: E=Sophos;i="5.84,281,1620716400"; d="scan'208";a="276823009" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jul 2021 00:18:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.84,281,1620716400"; d="scan'208";a="664728415" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.151]) by fmsmga006.fm.intel.com with ESMTP; 30 Jul 2021 00:18:41 -0700 Date: Fri, 30 Jul 2021 15:18:40 +0800 From: Feng Tang To: Michal Hocko Cc: linux-mm@kvack.org, Andrew Morton , David Rientjes , Dave Hansen , Ben Widawsky , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Andrea Arcangeli , Mel Gorman , Mike Kravetz , Randy Dunlap , Vlastimil Babka , Andi Kleen , Dan Williams , ying.huang@intel.com, Dave Hansen Subject: Re: [PATCH v6 1/6] mm/mempolicy: Add MPOL_PREFERRED_MANY for multiple preferred nodes Message-ID: <20210730071840.GA87305@shbuild999.sh.intel.com> References: <1626077374-81682-2-git-send-email-feng.tang@intel.com> <20210728141156.GC43486@shbuild999.sh.intel.com> <20210729070918.GA96680@shbuild999.sh.intel.com> <20210729151242.GA42865@shbuild999.sh.intel.com> <20210730030502.GA87066@shbuild999.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 30, 2021 at 08:36:50AM +0200, Michal Hocko wrote: > On Fri 30-07-21 11:05:02, Feng Tang wrote: > > On Thu, Jul 29, 2021 at 06:21:19PM +0200, Michal Hocko wrote: > > > On Thu 29-07-21 23:12:42, Feng Tang wrote: > > > > On Thu, Jul 29, 2021 at 03:38:44PM +0200, Michal Hocko wrote: > > > [...] > > > > > Also the > > > > > semantic to give nodes some ordering based on their numbers sounds > > > > > rather weird to me. > > > > > > > > I agree, and as I admitted in the first reply, this need to be fixed. > > > > > > OK. I was not really clear that we are on the same page here. > > > > > > > > The semantic I am proposing is to allocate from prefered nodes in > > > > > distance order starting from the local node. > > > > > > > > So the plan is: > > > > * if the local node is set in 'prefer-many's nodemask, then chose > > > > * otherwise chose the node with the shortest distance to local node > > > > ? > > > > > > Yes and what I am trying to say is that you will achieve that simply by > > > doing the following in policy_node: > > > if (policy->mode == MPOL_PREFERRED_MANY) > > > return nd; > > > > One thing is, it's possible that 'nd' is not set in the preferred > > nodemask. > > Yes, and there shouldn't be any problem with that. The given node is > only used to get the respective zonelist (order distance ordered list of > zones to try). get_page_from_freelist will then use the preferred node > mask to filter this zone list. Is that more clear now? Yes, from the code, the policy_node() is always coupled with policy_nodemask(), which secures the 'nodemask' limit. Thanks for the clarification! And for the mempolicy_slab_node(), it seems to be a little different, and we may need to reuse its logic for 'bind' policy, which is similar to what we've discussed, pick a nearest node to the local node. And similar for mpol_misplaced(). Thoughts? Thanks, Feng > -- > Michal Hocko > SUSE Labs