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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 2CA69C11D00 for ; Fri, 21 Feb 2020 00:40:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2964208CD for ; Fri, 21 Feb 2020 00:40:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582245637; bh=hZ3dGT7YJqIbKFGjdrNH8loYD4/AxKe4J06eOSLcC6E=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=i8kQn3rNUFA65RBGvUwkuxxIQIoT667fQuYCc+SjFLAA4VoIUq4ZffdJEBOcu4zLu 1X3SM86M9cogSnCOAYxGkxcf4vyXP2lrJRXl/ML04Sxerd5ImMyT7i1zDUjUz5oblO 7/2lyNaDf9mzQOJpspPaihLpMWxYTihI6m92FyTE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729530AbgBUAkf (ORCPT ); Thu, 20 Feb 2020 19:40:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:46134 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729365AbgBUAke (ORCPT ); Thu, 20 Feb 2020 19:40:34 -0500 Received: from X1 (nat-ab2241.sltdut.senawave.net [162.218.216.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2C38E207FD; Fri, 21 Feb 2020 00:40:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582245634; bh=hZ3dGT7YJqIbKFGjdrNH8loYD4/AxKe4J06eOSLcC6E=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Vuni54K9568CmSjIYiNas2JBby91Xm/1JOEwM+Akreo8FEcnNdjw92J3r4Fgby+jT pk1so+82is8MWqD5UAYuxK8geIwlA1LW/FFWhOJ7lJ6iSyVYSX7n9NrgY9EQhl3s+p gULzSpzkWR1r5ADD8iZLWgU8yMj0xEGsqFnKxTfI= Date: Thu, 20 Feb 2020 16:40:33 -0800 From: Andrew Morton To: Joel Savitz Cc: linux-kernel@vger.kernel.org, Rafael Aquini , linux-mm@kvack.org Subject: Re: [PATCH] mm/page_alloc: increase default min_free_kbytes bound Message-Id: <20200220164033.8634c2c836c1558daebd81b9@linux-foundation.org> In-Reply-To: <20200220150103.5183-1-jsavitz@redhat.com> References: <20200220150103.5183-1-jsavitz@redhat.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 20 Feb 2020 10:01:03 -0500 Joel Savitz wrote: > > Currently, the vm.min_free_kbytes sysctl value is capped at a hardcoded > 64M in init_per_zone_wmark_min (unless it is overridden by khugepaged > initialization). > > This value has not been modified since 2005, and enterprise-grade > systems now frequently have hundreds of GB of RAM and multiple 10, 40, > or even 100 GB NICs. We have seen page allocation failures on heavily > loaded systems related to NIC drivers. These issues were resolved by an > increase to vm.min_free_kbytes. > > This patch increases the hardcoded value by a factor of 4 as a temporary > solution. OK, better than nothing I guess. > Further work to make the calculation of vm.min_free_kbytes more > consistent throughout the kernel would be desirable. > > As an example of the inconsistency of the current method, this value is > recalculated by init_per_zone_wmark_min() in the case of memory hotplug > which will override the value set by set_recommended_min_free_kbytes() > called during khugepaged initialization even if khugepaged remains > enabled, however an on/off toggle of khugepaged will then recalculate > and set the value via set_recommended_min_free_kbytes(). > Yup, these hardcoded numbers are lame.