From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935813AbcIUS1v (ORCPT ); Wed, 21 Sep 2016 14:27:51 -0400 Received: from mga01.intel.com ([192.55.52.88]:50247 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934418AbcIUS1u (ORCPT ); Wed, 21 Sep 2016 14:27:50 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,374,1470726000"; d="scan'208";a="11899022" Subject: Re: [PATCH 0/1] memory offline issues with hugepage size > memory block size To: Michal Hocko , Mike Kravetz References: <20160920155354.54403-1-gerald.schaefer@de.ibm.com> <20160921182054.GK24210@dhcp22.suse.cz> Cc: Gerald Schaefer , Andrew Morton , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A . Shutemov" , Vlastimil Babka , "Aneesh Kumar K . V" , Martin Schwidefsky , Heiko Carstens , Rui Teng From: Dave Hansen Message-ID: <57E2D124.9000108@linux.intel.com> Date: Wed, 21 Sep 2016 11:27:48 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: <20160921182054.GK24210@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/21/2016 11:20 AM, Michal Hocko wrote: > I would even question the per page block offlining itself. Why would > anybody want to offline few blocks rather than the whole node? What is > the usecase here? The original reason was so that you could remove a DIMM or a riser card full of DIMMs, which are certainly a subset of a node. With virtual machines, perhaps you only want to make a small adjustment to the memory that a VM has. Or, perhaps the VM only _has_ one node. Granted, ballooning takes care of a lot of these cases, but memmap[] starts to get annoying at some point if you balloon too much memory away. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f69.google.com (mail-pa0-f69.google.com [209.85.220.69]) by kanga.kvack.org (Postfix) with ESMTP id CEE9C6B0279 for ; Wed, 21 Sep 2016 14:27:49 -0400 (EDT) Received: by mail-pa0-f69.google.com with SMTP id wk8so106157091pab.3 for ; Wed, 21 Sep 2016 11:27:49 -0700 (PDT) Received: from mga03.intel.com (mga03.intel.com. [134.134.136.65]) by mx.google.com with ESMTPS id d186si76836665pfc.72.2016.09.21.11.27.48 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 21 Sep 2016 11:27:49 -0700 (PDT) Subject: Re: [PATCH 0/1] memory offline issues with hugepage size > memory block size References: <20160920155354.54403-1-gerald.schaefer@de.ibm.com> <20160921182054.GK24210@dhcp22.suse.cz> From: Dave Hansen Message-ID: <57E2D124.9000108@linux.intel.com> Date: Wed, 21 Sep 2016 11:27:48 -0700 MIME-Version: 1.0 In-Reply-To: <20160921182054.GK24210@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Mike Kravetz Cc: Gerald Schaefer , Andrew Morton , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A . Shutemov" , Vlastimil Babka , "Aneesh Kumar K . V" , Martin Schwidefsky , Heiko Carstens , Rui Teng On 09/21/2016 11:20 AM, Michal Hocko wrote: > I would even question the per page block offlining itself. Why would > anybody want to offline few blocks rather than the whole node? What is > the usecase here? The original reason was so that you could remove a DIMM or a riser card full of DIMMs, which are certainly a subset of a node. With virtual machines, perhaps you only want to make a small adjustment to the memory that a VM has. Or, perhaps the VM only _has_ one node. Granted, ballooning takes care of a lot of these cases, but memmap[] starts to get annoying at some point if you balloon too much memory away. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org