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 F2E27C432C3 for ; Wed, 3 Mar 2021 19:29:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF7B464EFC for ; Wed, 3 Mar 2021 19:29:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1580606AbhCCSed (ORCPT ); Wed, 3 Mar 2021 13:34:33 -0500 Received: from mx2.suse.de ([195.135.220.15]:50594 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242699AbhCCRPz (ORCPT ); Wed, 3 Mar 2021 12:15:55 -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=1614791673; 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=q26pRxbPLPeAXKwpbYB/VBIDOB+tOVBn79NxDJnUl5g=; b=ulDJEW5PWSWbah35Ay3Wzr14xuwpkgj3FXThrmpCCRfgSUMued8Gv0LNVopopO5FUrIHLH BBJzcRQVexqqI5ctshpuqwBeBGVigHx/Ykxm6dV4E7CWvY1g/uLSmTRpyMWnIxEvgtfEMP CmporA3rIxsdAc8vzRKMJrU+6vTrqdk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2B89BACBC; Wed, 3 Mar 2021 17:14:33 +0000 (UTC) Date: Wed, 3 Mar 2021 18:14:30 +0100 From: Michal Hocko To: Ben Widawsky Cc: Feng Tang , "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" , 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> <20210303134644.GC78458@shbuild999.sh.intel.com> <20210303163141.v5wu2sfo2zj2qqsw@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210303163141.v5wu2sfo2zj2qqsw@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 03-03-21 08:31:41, Ben Widawsky wrote: > On 21-03-03 14:59:35, Michal Hocko wrote: > > On Wed 03-03-21 21:46:44, Feng Tang wrote: > > > On Wed, Mar 03, 2021 at 09:18:32PM +0800, Tang, Feng 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: > > [...] > > > > > > 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. > > > > > > I just double checked by rerun the test, 'gfp_mask &= ~__GFP_DIRECT_RECLAIM' > > > can also accelerate the allocation much! though is still a little slower than > > > this patch. Seems I've messed some of the tries, and sorry for the confusion! > > > > > > Could this be used as the solution? or the adding another fallback_nodemask way? > > > but the latter will change the current API quite a bit. > > > > I haven't got to the whole series yet. The real question is whether the > > first attempt to enforce the preferred mask is a general win. I would > > argue that it resembles the existing single node preferred memory policy > > because that one doesn't push heavily on the preferred node either. So > > dropping just the direct reclaim mode makes some sense to me. > > > > IIRC this is something I was recommending in an early proposal of the > > feature. > > My assumption [FWIW] is that the usecases we've outlined for multi-preferred > would want more heavy pushing on the preference mask. However, maybe the uapi > could dictate how hard to try/not try. What does that mean and what is the expectation from the kernel to be more or less cast in stone? -- Michal Hocko SUSE Labs