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=-5.4 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 93E4AC433E0 for ; Thu, 4 Feb 2021 09:33:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0972264F48 for ; Thu, 4 Feb 2021 09:33:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0972264F48 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6AE3F6B0005; Thu, 4 Feb 2021 04:33:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 65F2D6B006C; Thu, 4 Feb 2021 04:33:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 575876B006E; Thu, 4 Feb 2021 04:33:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0122.hostedemail.com [216.40.44.122]) by kanga.kvack.org (Postfix) with ESMTP id 43DEC6B0005 for ; Thu, 4 Feb 2021 04:33:50 -0500 (EST) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 0656F8249980 for ; Thu, 4 Feb 2021 09:33:50 +0000 (UTC) X-FDA: 77780073420.01.tent30_4d07841275db Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id D95C110046461 for ; Thu, 4 Feb 2021 09:33:49 +0000 (UTC) X-HE-Tag: tent30_4d07841275db X-Filterd-Recvd-Size: 3067 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf04.hostedemail.com (Postfix) with ESMTP for ; Thu, 4 Feb 2021 09:33:49 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EF8F4AC97; Thu, 4 Feb 2021 09:33:47 +0000 (UTC) Subject: Re: [RFC PATCH v0] mm/slub: Let number of online CPUs determine the slub page order To: bharata@linux.ibm.com Cc: Christoph Lameter , Will Deacon , Vincent Guittot , linux-kernel , linux-mm@kvack.org, David Rientjes , Joonsoo Kim , Andrew Morton , guro@fb.com, Shakeel Butt , Johannes Weiner , aneesh.kumar@linux.ibm.com, Jann Horn , Michal Hocko , Catalin Marinas References: <786571e7-b9a2-4cdb-06d5-aa4a4b439b7e@suse.cz> <20210123051607.GC2587010@in.ibm.com> <66652406-25e4-a9e7-45a1-8ad14d2e8a36@suse.cz> <20210126230305.GD30941@willie-the-truck> <81424d71-c479-4c4a-de14-0a9b3f636e23@suse.cz> <20210203111009.GB2869122@in.ibm.com> From: Vlastimil Babka Message-ID: Date: Thu, 4 Feb 2021 10:33:47 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210203111009.GB2869122@in.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 2/3/21 12:10 PM, Bharata B Rao wrote: > On Wed, Jan 27, 2021 at 12:04:01PM +0100, Vlastimil Babka wrote: >> Yes, but it's tricky to do the retuning safely, e.g. if freelist randomization >> is enabled, see [1]. >> >> But as a quick fix for the regression, the heuristic idea could work reasonably >> on all architectures? >> - if num_present_cpus() is > 1, trust that it doesn't have the issue such as >> arm64, and use it >> - otherwise use nr_cpu_ids >> >> Long-term we can attempt to do the retuning safe, or decide that number of cpus >> shouldn't determine the order... >> >> [1] https://lore.kernel.org/linux-mm/d7fb9425-9a62-c7b8-604d-5828d7e6b1da@suse.cz/ > > So what is preferrable here now? Above or other quick fix or reverting > the original commit? I would try the above first. In case it doesn't work, revert. As the immediate fix for the regression, that people can safely backport. Anything more complex will take more time and would be more risky to backport. > Regards, > Bharata. >