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=-1.0 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS 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 865B8C43143 for ; Tue, 11 Sep 2018 02:02:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B8C720854 for ; Tue, 11 Sep 2018 02:02:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B8C720854 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726554AbeIKG7O (ORCPT ); Tue, 11 Sep 2018 02:59:14 -0400 Received: from mailout.easymail.ca ([64.68.200.34]:58820 "EHLO mailout.easymail.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726194AbeIKG7N (ORCPT ); Tue, 11 Sep 2018 02:59:13 -0400 Received: from localhost (localhost [127.0.0.1]) by mailout.easymail.ca (Postfix) with ESMTP id 261A4C0894; Tue, 11 Sep 2018 02:02:21 +0000 (UTC) Received: from mailout.easymail.ca ([127.0.0.1]) by localhost (emo01-pco.easydns.vpn [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id M7CMylfw2hou; Tue, 11 Sep 2018 02:02:21 +0000 (UTC) Received: from [192.168.1.87] (c-24-9-64-241.hsd1.co.comcast.net [24.9.64.241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mailout.easymail.ca (Postfix) with ESMTPSA id 972A1C067C; Tue, 11 Sep 2018 02:02:06 +0000 (UTC) Subject: Re: [PATCH] arm64: add NUMA emulation support To: Michal Hocko Cc: Will Deacon , catalin.marinas@arm.com, sudeep.holla@arm.com, ganapatrao.kulkarni@cavium.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Shuah Khan References: <20180824230559.32336-1-shuah@kernel.org> <20180828174011.GE20375@arm.com> <20180829110802.GD10349@dhcp22.suse.cz> <20180905064252.GW14951@dhcp22.suse.cz> <20180907083452.GC19621@dhcp22.suse.cz> <20180910134845.GH10951@dhcp22.suse.cz> From: Shuah Khan Message-ID: <4d7beb50-f778-507a-4c3c-f6de92f8cfb9@kernel.org> Date: Mon, 10 Sep 2018 20:02:05 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180910134845.GH10951@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Michal, On 09/10/2018 07:48 AM, Michal Hocko wrote: > On Fri 07-09-18 16:30:59, Shuah Khan wrote: >> On 09/07/2018 02:34 AM, Michal Hocko wrote: >>> On Thu 06-09-18 15:53:34, Shuah Khan wrote: [....] >> >> In addition to isolation, being able to reserve a block instead is one of the >> issues I am looking to address. Unfortunately memory cgroups won't address that >> issue. > > Could you be more specific why you need reservations other than > isolation. > Taking automotive as a specific example, there are two classes of applications: 1. critical applications that must run 2. Infotainment and misc. user-space. In this case, being able to reserve a block of memory for critical applications will ensure the memory is available for them. If a critical application has to restart and/or when an on-demand critical application starts, it might not be able to allocate memory if it is not reserved. When a flat system has multiple memory blocks, with NUMA emulation in conjunction with cpusets, one or more block can be reserved for critical applications configuring a set of cpus and one of more memory nodes for them. Memory cgroups will not support such reservation. Hope this helps explain the use-case I am trying to address with this patch. thanks, -- Shuah