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=-3.8 required=3.0 tests=BAYES_00, 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 B58C5C433E0 for ; Wed, 3 Mar 2021 20:56:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 86B8664F0D for ; Wed, 3 Mar 2021 20:56:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386659AbhCCSpS (ORCPT ); Wed, 3 Mar 2021 13:45:18 -0500 Received: from mga04.intel.com ([192.55.52.120]:55554 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232816AbhCCRXh (ORCPT ); Wed, 3 Mar 2021 12:23:37 -0500 IronPort-SDR: eeWUMD5TmW44ehesPTe0dDv3zRkGFeu22ePdMUC1BgZBId4XPB5SRxhIFoqXjxWsstSaTkiqzS cr324eVhKYFQ== X-IronPort-AV: E=McAfee;i="6000,8403,9912"; a="184826045" X-IronPort-AV: E=Sophos;i="5.81,220,1610438400"; d="scan'208";a="184826045" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Mar 2021 09:22:53 -0800 IronPort-SDR: QCMEmJVGU4YRIlf3c8nrQuc6htZOOa+ZRn+Sspn6ODAOJkoxoLLiK0AydEmNBGlFp5GTZYixn3 KkjqwcEajcnQ== X-IronPort-AV: E=Sophos;i="5.81,220,1610438400"; d="scan'208";a="600227031" Received: from tsaijane-mobl.amr.corp.intel.com (HELO intel.com) ([10.252.136.84]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Mar 2021 09:22:52 -0800 Date: Wed, 3 Mar 2021 09:22:50 -0800 From: Ben Widawsky To: Michal Hocko 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: <20210303172250.wbp47skyuf6r37wi@intel.com> Mail-Followup-To: Michal Hocko , 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" References: <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: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21-03-03 18:14:30, Michal Hocko wrote: > 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? > (I'm not positive I've understood your question, so correct me if I misunderstood) I'm not sure there is a stone-cast way to define it nor should we. At the very least though, something in uapi that has a general mapping to GFP flags (specifically around reclaim) for the first round of allocation could make sense. In my head there are 3 levels of request possible for multiple nodes: 1. BIND: Those nodes or die. 2. Preferred hard: Those nodes and I'm willing to wait. Fallback if impossible. 3. Preferred soft: Those nodes but I don't want to wait. Current UAPI in the series doesn't define a distinction between 2, and 3. As I understand the change, Feng is defining the behavior to be #3, which makes #2 not an option. I sort of punted on defining it entirely, in the beginning.