From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751932AbdB0Lyh (ORCPT ); Mon, 27 Feb 2017 06:54:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44280 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751673AbdB0Lyf (ORCPT ); Mon, 27 Feb 2017 06:54:35 -0500 From: Vitaly Kuznetsov To: Heiko Carstens Cc: Michal Hocko , linux-mm@kvack.org, Andrew Morton , Greg KH , "K. Y. Srinivasan" , David Rientjes , Daniel Kiper , linux-api@vger.kernel.org, LKML , linux-s390@vger.kernel.org, xen-devel@lists.xenproject.org, linux-acpi@vger.kernel.org, Michal Hocko Subject: Re: [RFC PATCH] mm, hotplug: get rid of auto_online_blocks References: <20170227092817.23571-1-mhocko@kernel.org> <87lgssvtni.fsf@vitty.brq.redhat.com> <20170227112510.GA4129@osiris> Date: Mon, 27 Feb 2017 12:50:19 +0100 In-Reply-To: <20170227112510.GA4129@osiris> (Heiko Carstens's message of "Mon, 27 Feb 2017 12:25:10 +0100") Message-ID: <87a897x37o.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 27 Feb 2017 11:50:23 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Heiko Carstens writes: > On Mon, Feb 27, 2017 at 11:02:09AM +0100, Vitaly Kuznetsov wrote: >> A couple of other thoughts: >> 1) Having all newly added memory online ASAP is probably what people >> want for all virtual machines. Sorry, obviously missed 'x86' in the above statement. > > This is not true for s390. On s390 we have "standby" memory that a guest > sees and potentially may use if it sets it online. Every guest that sets > memory offline contributes to the hypervisor's standby memory pool, while > onlining standby memory takes memory away from the standby pool. > > The use-case is that a system administrator in advance knows the maximum > size a guest will ever have and also defines how much memory should be used > at boot time. The difference is standby memory. > > Auto-onlining of standby memory is the last thing we want. > This is actually a very good example of why we need the config option. s390 kernels will have it disabled. -- Vitaly