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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 EDEECC43142 for ; Wed, 3 Mar 2021 16:09:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D575564EE9 for ; Wed, 3 Mar 2021 16:09:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383678AbhCCQI6 (ORCPT ); Wed, 3 Mar 2021 11:08:58 -0500 Received: from mx2.suse.de ([195.135.220.15]:47150 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233560AbhCCLlL (ORCPT ); Wed, 3 Mar 2021 06:41:11 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1614771603; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/0ADgNDESPnWNN/oQj1Z1pQMpSA2u1PUuIFJNPh0PdE=; b=Z0fL32v3uoFnrNsSJM9jrH3D21lchZOXqg4FNMgPgDbtpu5U788eCxH1oCmNVg1XaVsxYH 9QgruwEJImbeNT8nSyzGT6JMKK8mKcUmGMp16k8xoLVRyFxC6UzQXgz7i96xFnNZuWAtEE smv6eJrU6mX6+yiKxXJ1pH6R1JcMvyA= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7FD99AD5C; Wed, 3 Mar 2021 11:40:03 +0000 (UTC) Date: Wed, 3 Mar 2021 12:39:57 +0100 From: Michal Hocko To: Feng Tang 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: 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: <1614766858-90344-15-git-send-email-feng.tang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? -- Michal Hocko SUSE Labs