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 523F1C4332D for ; Wed, 3 Mar 2021 16:52:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DDC564ED4 for ; Wed, 3 Mar 2021 16:52:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378628AbhCCQuV (ORCPT ); Wed, 3 Mar 2021 11:50:21 -0500 Received: from mga06.intel.com ([134.134.136.31]:62514 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347049AbhCCMWB (ORCPT ); Wed, 3 Mar 2021 07:22:01 -0500 IronPort-SDR: 5vkIaYlT9PvryjaN9oSvZT/3OYgt6WCL8ORCXwgFL+PbHpBYpmYYH0TMLfIV7a5S0bXkWzs/P7 KKvgE1Boga9g== X-IronPort-AV: E=McAfee;i="6000,8403,9911"; a="248586096" X-IronPort-AV: E=Sophos;i="5.81,219,1610438400"; d="scan'208";a="248586096" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Mar 2021 04:18:38 -0800 IronPort-SDR: cRQHE4dwnBcO/xokC6rHvSqyWGEhRUBHHUv7a/QcZQ0+uiaz2tdKHblqcLeqor0l8lYzPKxOjE QIOm1zeBtN9w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,219,1610438400"; d="scan'208";a="445230170" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.165]) by orsmga001.jf.intel.com with ESMTP; 03 Mar 2021 04:18:34 -0800 Date: Wed, 3 Mar 2021 20:18:33 +0800 From: Feng Tang To: Michal Hocko Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Andrea Arcangeli , David Rientjes , Mel Gorman , Mike Kravetz , Randy Dunlap , Vlastimil Babka , "Hansen, Dave" , "Widawsky, Ben" , Andi leen , "Williams, Dan J" Subject: Re: [PATCH v3 RFC 14/14] mm: speedup page alloc for MPOL_PREFERRED_MANY by adding a NO_SLOWPATH gfp bit Message-ID: <20210303121833.GB16736@shbuild999.sh.intel.com> References: <1614766858-90344-1-git-send-email-feng.tang@intel.com> <1614766858-90344-15-git-send-email-feng.tang@intel.com> <20210303120717.GA16736@shbuild999.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210303120717.GA16736@shbuild999.sh.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 03, 2021 at 08:07:17PM +0800, Tang, Feng wrote: > Hi Michal, > > On Wed, Mar 03, 2021 at 12:39:57PM +0100, Michal Hocko wrote: > > On Wed 03-03-21 18:20:58, Feng Tang wrote: > > > When doing broader test, we noticed allocation slowness in one test > > > case that malloc memory with size which is slightly bigger than free > > > memory of targeted nodes, but much less then the total free memory > > > of system. > > > > > > The reason is the code enters the slowpath of __alloc_pages_nodemask(), > > > which takes quite some time. As alloc_pages_policy() will give it a 2nd > > > try with NULL nodemask, so there is no need to enter the slowpath for > > > the first try. Add a new gfp bit to skip the slowpath, so that user cases > > > like this can leverage. > > > > > > With it, the malloc in such case is much accelerated as it never enters > > > the slowpath. > > > > > > Adding a new gfp_mask bit is generally not liked, and another idea is to > > > add another nodemask to struct 'alloc_context', so it has 2: 'preferred-nmask' > > > and 'fallback-nmask', and they will be tried in turn if not NULL, with > > > it we can call __alloc_pages_nodemask() only once. > > > > Yes, it is very much disliked. Is there any reason why you cannot use > > GFP_NOWAIT for that purpose? > > I did try that at the first place, but it didn't obviously change the slowness. > I assumed the direct claim was still involved as GFP_NOWAIT only impact kswapd > reclaim. One thing I tried which can fix the slowness is: + gfp_mask &= ~(__GFP_DIRECT_RECLAIM | __GFP_KSWAPD_RECLAIM); which explicitly clears the 2 kinds of reclaim. And I thought it's too hacky and didn't mention it in the commit log. Thanks, Feng