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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 A7CC7C04ABB for ; Tue, 11 Sep 2018 09:11:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6D8E520854 for ; Tue, 11 Sep 2018 09:11:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6D8E520854 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 S1727051AbeIKOJt (ORCPT ); Tue, 11 Sep 2018 10:09:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:60242 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726739AbeIKOJt (ORCPT ); Tue, 11 Sep 2018 10:09:49 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id C426AAF8A; Tue, 11 Sep 2018 09:11:24 +0000 (UTC) Date: Tue, 11 Sep 2018 11:11:24 +0200 From: Michal Hocko To: Shuah Khan 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 Subject: Re: [PATCH] arm64: add NUMA emulation support Message-ID: <20180911091124.GP10951@dhcp22.suse.cz> References: <20180828174011.GE20375@arm.com> <20180829110802.GD10349@dhcp22.suse.cz> <20180905064252.GW14951@dhcp22.suse.cz> <20180907083452.GC19621@dhcp22.suse.cz> <20180910134845.GH10951@dhcp22.suse.cz> <4d7beb50-f778-507a-4c3c-f6de92f8cfb9@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d7beb50-f778-507a-4c3c-f6de92f8cfb9@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 10-09-18 20:02:05, Shuah Khan wrote: > 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. OK, that is more clear. I still believe that you either have to have a very good control over memory allocations or a good luck to not see unexpected kernel allocations in your reserved memory which might easily break guarantees you would like to accomplish. -- Michal Hocko SUSE Labs