From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from song.cn.fujitsu.com (unknown [222.73.24.84]) by ozlabs.org (Postfix) with ESMTP id CD0142C0294 for ; Thu, 7 Feb 2013 18:57:26 +1100 (EST) Message-ID: <51135E33.4060508@cn.fujitsu.com> Date: Thu, 07 Feb 2013 15:56:35 +0800 From: Tang Chen MIME-Version: 1.0 To: Glauber Costa Subject: Re: [PATCH v5 01/14] memory-hotplug: try to offline the memory twice to avoid dependence References: <1356350964-13437-1-git-send-email-tangchen@cn.fujitsu.com> <1356350964-13437-2-git-send-email-tangchen@cn.fujitsu.com> <50D96543.6010903@parallels.com> <50DFD7F7.5090408@cn.fujitsu.com> <50ED8834.1090804@parallels.com> <5111C8EB.6090805@cn.fujitsu.com> <51121FB7.1070205@cn.fujitsu.com> <51122C1D.5020002@cn.fujitsu.com> <5112679A.7080600@parallels.com> In-Reply-To: <5112679A.7080600@parallels.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, linux-mm@kvack.org, paulus@samba.org, hpa@zytor.com, sparclinux@vger.kernel.org, cl@linux.com, linux-s390@vger.kernel.org, x86@kernel.org, linux-acpi@vger.kernel.org, isimatu.yasuaki@jp.fujitsu.com, linfeng@cn.fujitsu.com, mgorman@suse.de, kosaki.motohiro@jp.fujitsu.com, rientjes@google.com, liuj97@gmail.com, len.brown@intel.com, Miao Xie , Wen Congyang , cmetcalf@tilera.com, wujianguo@huawei.com, yinghai@kernel.org, KAMEZAWA Hiroyuki , laijs@cn.fujitsu.com, linux-kernel@vger.kernel.org, minchan.kim@gmail.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 02/06/2013 10:24 PM, Glauber Costa wrote: >>>> And one more question, a memory section is 128MB in Linux. If we reserve >>>> part of the them for page_cgroup, >>>> then anyone who wants to allocate a contiguous memory larger than 128MB, >>>> it will fail, right ? >>>> Is it OK ? > No, it is not. > > Another take on this: Can't we free all the page_cgroup structure before > we actually start removing the sections ? If we do this, we would be > basically left with no problem at all, since when your code starts > running we would no longer have any page_cgroup allocated. > > All you have to guarantee is that it happens after the memory block is > already isolated and allocations no longer can reach it. > > What do you think ? Hi Glauber, I don't think so. We can offline some of the sections and leave the reset online. For example, we store page_cgroups of memory9~11 in memory8. So when we offline memory8, we free memory8's page_cgroup storing on other section, but we cannot free the page_cgroups being stored in memory8 if memory9~11 are left online. So we still need to offline memory9~11, and then offline memory8, right ? I think it makes no difference. Thanks. :)