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 083A7C433E0 for ; Wed, 3 Mar 2021 13:53:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7F5E364EE8 for ; Wed, 3 Mar 2021 13:53:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F5E364EE8 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DEAD28D016A; Wed, 3 Mar 2021 08:53:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D9AF38D0157; Wed, 3 Mar 2021 08:53:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C3CC68D016A; Wed, 3 Mar 2021 08:53:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0152.hostedemail.com [216.40.44.152]) by kanga.kvack.org (Postfix) with ESMTP id A84AF8D0157 for ; Wed, 3 Mar 2021 08:53:57 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 638F8180AD822 for ; Wed, 3 Mar 2021 13:53:57 +0000 (UTC) X-FDA: 77878706514.16.58CB813 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf08.hostedemail.com (Postfix) with ESMTP id DCB9C80192ED for ; Wed, 3 Mar 2021 13:53:54 +0000 (UTC) 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=1614779635; 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=/TQ2RBE4z055fHuqnHKpsqZTckQoxi2cA1K9u68p52Q=; b=lvmW7MB8x0GNReTSj5AlI+rASO06gPQjinfsV5RewgY/1x/JC7XrC3n3GdheHnzfV987T0 oKYnFcPbQXMTqF61TtWx92lbr7IwXIDShKnbZmKvKKjIrjStLXAE8qNjv2lqzEF7zJo7tS YAk97XZ/ah1WS7hoJKzMr3beKMPEbVk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 285F2AC24; Wed, 3 Mar 2021 13:53:55 +0000 (UTC) Date: Wed, 3 Mar 2021 14:53:54 +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 , "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: 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> <20210303121833.GB16736@shbuild999.sh.intel.com> <20210303131832.GB78458@shbuild999.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210303131832.GB78458@shbuild999.sh.intel.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DCB9C80192ED X-Stat-Signature: cp131fg5rhgmcrnhs1jt3yat51pk7rrk Received-SPF: none (suse.com>: No applicable sender policy available) receiver=imf08; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614779634-923388 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 03-03-21 21:18:32, Feng Tang wrote: > On Wed, Mar 03, 2021 at 01:32:11PM +0100, Michal Hocko wrote: > > On Wed 03-03-21 20:18:33, Feng Tang wrote: > > > 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. > > > > I assume you haven't really created gfp mask correctly. What was the > > exact gfp mask you have used? > > The testcase is a malloc with multi-preferred-node policy, IIRC, the gfp > mask is HIGHUSER_MOVABLE originally, and code here ORs (__GFP_RETRY_MAYFAIL | __GFP_NOWARN). > > As GFP_WAIT == __GFP_KSWAPD_RECLAIM, in this test case, the bit is already set. Yes, you have to clear the gfp flag for the direct reclaim. I can see how that can be confusing though > > > 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. > > > > Clearing __GFP_DIRECT_RECLAIM would be the right way to achieve > > GFP_NOWAIT semantic. Why would you want to exclude kswapd as well? > > When I tried gfp_mask &= ~__GFP_DIRECT_RECLAIM, the slowness couldn't > be fixed. OK, I thought that you wanted to prevent the direct reclaim because that is the usual suspect for a slow down. If this is not not related to the direct reclaim then please try to find out what the acutal bottle neck is. Also how big of a slowdown are we talking about here? -- Michal Hocko SUSE Labs