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,NICE_REPLY_A,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 54E9BC433E0 for ; Fri, 5 Mar 2021 17:38:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D248C65090 for ; Fri, 5 Mar 2021 17:38:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D248C65090 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 635E16B0073; 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a="167590572" X-IronPort-AV: E=Sophos;i="5.81,225,1610438400"; d="scan'208";a="167590572" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Mar 2021 09:38:10 -0800 IronPort-SDR: ufh/QpfAm7ZSxL27WcyXGy81bGyZbwKChF0AegqD/+wKS87uzt66c2UXCuUDUMX4L/fhW41Tsc lytGZCQBHoTQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,225,1610438400"; d="scan'208";a="446288784" Received: from viggo.jf.intel.com (HELO ray) ([10.54.77.144]) by orsmga001.jf.intel.com with ESMTP; 05 Mar 2021 09:38:09 -0800 Received: from [127.0.0.1] (localhost [127.0.0.1]) by ray (Postfix) with ESMTP id 5B99FE0A05; Wed, 3 Mar 2021 08:48:58 -0800 (PST) Subject: Re: [PATCH v3 RFC 14/14] mm: speedup page alloc for MPOL_PREFERRED_MANY by adding a NO_SLOWPATH gfp bit 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 , Andi leen , "Williams, Dan J" 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> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210303163141.v5wu2sfo2zj2qqsw@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Stat-Signature: fi4jhibwtp3ni1a1y6cfs7yjyebm5dh3 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A791C2000DA0 Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from=""; helo=mga17.intel.com; client-ip=192.55.52.151 X-HE-DKIM-Result: none/none X-HE-Tag: 1614965892-715608 Content-Transfer-Encoding: quoted-printable 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 3/3/21 8:31 AM, Ben Widawsky wrote: >> I haven't got to the whole series yet. The real question is whether th= e >> first attempt to enforce the preferred mask is a general win. I would >> argue that it resembles the existing single node preferred memory poli= cy >> 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-pref= erred > would want more heavy pushing on the preference mask. However, maybe th= e uapi > could dictate how hard to try/not try. There are two things that I think are important: 1. MPOL_PREFERRED_MANY fallback away from the preferred nodes should be *temporary*, even in the face of the preferred set being full. That means that _some_ reclaim needs to be done. Kicking off kswapd is fine for this. 2. MPOL_PREFERRED_MANY behavior should resemble MPOL_PREFERRED as closely as possible. We're just going to confuse users if they set a single node in a MPOL_PREFERRED_MANY mask and get different behavior from MPOL_PREFERRED. While it would be nice, short-term, to steer MPOL_PREFERRED_MANY behavior toward how we expect it to get used first, I think it's a mistake if we do it at the cost of long-term divergence from MPOL_PREFERR= ED.