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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 8294AC04FF3 for ; Fri, 21 May 2021 21:04:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 60043613EC for ; Fri, 21 May 2021 21:04:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229600AbhEUVFu (ORCPT ); Fri, 21 May 2021 17:05:50 -0400 Received: from mga05.intel.com ([192.55.52.43]:50407 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229503AbhEUVFt (ORCPT ); Fri, 21 May 2021 17:05:49 -0400 IronPort-SDR: iVLB4cvi0P4HT5CaJgkBt/Epq9njbF3jF2u87JGmisEuu79i6ngc2iSaH2EeHU2zlhIgSiOVrU 6ZSuSwAVIM2A== X-IronPort-AV: E=McAfee;i="6200,9189,9991"; a="287113214" X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="287113214" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 May 2021 14:04:26 -0700 IronPort-SDR: fuJVlCDPtDPU1LgaU3ik4C27vvmEHIhlCQNlsBKqvR92LtFmqgdAOvtFaG5/VfHfXzaq17ZfEa Z6bNgE3KA79w== X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="613379056" Received: from pburton-mobl.amr.corp.intel.com (HELO [10.209.36.169]) ([10.209.36.169]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 May 2021 14:04:25 -0700 Subject: Re: [PATCH 1/6] mm/page_alloc: Delete vm.percpu_pagelist_fraction To: Mel Gorman , Linux-MM Cc: Dave Hansen , Matthew Wilcox , Vlastimil Babka , Michal Hocko , Nicholas Piggin , LKML References: <20210521102826.28552-1-mgorman@techsingularity.net> <20210521102826.28552-2-mgorman@techsingularity.net> 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: <20210521102826.28552-2-mgorman@techsingularity.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/21/21 3:28 AM, Mel Gorman wrote: > The vm.percpu_pagelist_fraction is used to increase the batch and high > limits for the per-cpu page allocator (PCP). The intent behind the sysctl > is to reduce zone lock acquisition when allocating/freeing pages but it has > a problem. While it can decrease contention, it can also increase latency > on the allocation side due to unreasonably large batch sizes. This leads > to games where an administrator adjusts percpu_pagelist_fraction on the > fly to work around contention and allocation latency problems. > > This series aims to alleviate the problems with zone lock contention while > avoiding the allocation-side latency problems. For the purposes of review, > it's easier to remove this sysctl now and reintroduce a similar sysctl > later in the series that deals only with pcp->high. > > Signed-off-by: Mel Gorman I despise working with percpu_pagelist_fraction. I usually just end up poking random numbers into it and then checking what the fallout looks like in /proc/zoneinfo is. Good riddance. Acked-by: Dave Hansen