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 4005BC4361A for ; Wed, 3 Mar 2021 16:44:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B0DA64EBB for ; Wed, 3 Mar 2021 16:44:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1385050AbhCCQkf (ORCPT ); Wed, 3 Mar 2021 11:40:35 -0500 Received: from mga06.intel.com ([134.134.136.31]:61662 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233276AbhCCMI6 (ORCPT ); Wed, 3 Mar 2021 07:08:58 -0500 IronPort-SDR: BSUb33kdaXXbWOvoF8D9SVQB4nyCX2RiIWiPdS1HlGywuLA+LGe2hfjxSlDYbEE9TLQJmkoHYn W11N2ymVL3sQ== X-IronPort-AV: E=McAfee;i="6000,8403,9911"; a="248584691" X-IronPort-AV: E=Sophos;i="5.81,219,1610438400"; d="scan'208";a="248584691" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Mar 2021 04:07:21 -0800 IronPort-SDR: I52DGwf/24g4kchq4aEhWgOB3JotnW/SMkIuBQylgh2WGK7slV5xmQhYOKNPwvFbY/XAPQ4awF 50YHZlh8EvoA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,219,1610438400"; d="scan'208";a="383962001" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.165]) by orsmga002.jf.intel.com with ESMTP; 03 Mar 2021 04:07:17 -0800 Date: Wed, 3 Mar 2021 20:07:17 +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 , Dave Hansen , Ben Widawsky , Andi leen , Dan Williams Subject: Re: [PATCH v3 RFC 14/14] mm: speedup page alloc for MPOL_PREFERRED_MANY by adding a NO_SLOWPATH gfp bit Message-ID: <20210303120717.GA16736@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> 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 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. Thanks, Feng > -- > Michal Hocko > SUSE Labs