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 D3FBDC4707E for ; Fri, 21 May 2021 22:44:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA09D613D8 for ; Fri, 21 May 2021 22:44:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229968AbhEUWqU (ORCPT ); Fri, 21 May 2021 18:46:20 -0400 Received: from mga11.intel.com ([192.55.52.93]:31904 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229542AbhEUWqS (ORCPT ); Fri, 21 May 2021 18:46:18 -0400 IronPort-SDR: yxLfg//5PRRMEHDRRvh0UpJPZ8l03hVOvixMdJN68hxvjjJYjPcUWgQwOoKtSeIq/K83S3TzDS 3wwKeE3rvx+A== X-IronPort-AV: E=McAfee;i="6200,9189,9991"; a="198505230" X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="198505230" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 May 2021 15:44:52 -0700 IronPort-SDR: hPOy5o5jtVUZN4Cx027K97zYJf7w6YbFDuiX6t3Q8++aLrySPl8xbXidokjVMAzYnlgbUgy6x6 2vNi4NZ5eKTQ== X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="441126837" Received: from djayapra-mobl2.amr.corp.intel.com (HELO [10.212.209.34]) ([10.212.209.34]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 May 2021 15:44:52 -0700 Subject: Re: [PATCH 5/6] mm/page_alloc: Limit the number of pages on PCP lists when reclaim is active To: Mel Gorman , Linux-MM Cc: Dave Hansen , Matthew Wilcox , Vlastimil Babka , Michal Hocko , Nicholas Piggin , LKML References: <20210521102826.28552-1-mgorman@techsingularity.net> <20210521102826.28552-6-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: <20210521102826.28552-6-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: > +static int nr_pcp_high(struct per_cpu_pages *pcp, struct zone *zone) > +{ > + int high = READ_ONCE(pcp->high); > + > + if (unlikely(!high)) > + return 0; > + > + if (!test_bit(ZONE_RECLAIM_ACTIVE, &zone->flags)) > + return high; > + > + /* > + * If reclaim is active, limit the number of pages that can be > + * stored on pcp lists > + */ > + return READ_ONCE(pcp->batch) << 2; > +} Should there be a sanity check on this? Let's say we had one of those weirdo zones with tons of CPUs and a small low_wmark_pages(). Could we have a case where: pcp->high < pcp->batch<<2 and this effectively *raises* nr_pcp_high()? It's not possible with the current pcp->high calculation, but does anything prevent it now?