From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fgwmail5.fujitsu.co.jp (fgwmail5.fujitsu.co.jp [192.51.44.35]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 44B502C007E for ; Thu, 10 Jan 2013 18:32:48 +1100 (EST) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id E548B3EE0C0 for ; Thu, 10 Jan 2013 16:32:43 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id CC0D345DE54 for ; Thu, 10 Jan 2013 16:32:43 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id AC00D45DE53 for ; Thu, 10 Jan 2013 16:32:43 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 99EFC1DB803F for ; Thu, 10 Jan 2013 16:32:43 +0900 (JST) Received: from m1001.s.css.fujitsu.com (m1001.s.css.fujitsu.com [10.240.81.139]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 39E321DB802C for ; Thu, 10 Jan 2013 16:32:43 +0900 (JST) Message-ID: <50EE6E50.3040609@jp.fujitsu.com> Date: Thu, 10 Jan 2013 16:31:28 +0900 From: Kamezawa Hiroyuki MIME-Version: 1.0 To: Glauber Costa Subject: Re: [PATCH v6 00/15] memory-hotplug: hot-remove physical memory References: <1357723959-5416-1-git-send-email-tangchen@cn.fujitsu.com> <20130109142314.1ce04a96.akpm@linux-foundation.org> <50EE24A4.8020601@cn.fujitsu.com> <50EE6A48.7060307@parallels.com> In-Reply-To: <50EE6A48.7060307@parallels.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Tang Chen , 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, len.brown@intel.com, wency@cn.fujitsu.com, cmetcalf@tilera.com, wujianguo@huawei.com, yinghai@kernel.org, laijs@cn.fujitsu.com, linux-kernel@vger.kernel.org, minchan.kim@gmail.com, Andrew Morton , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , (2013/01/10 16:14), Glauber Costa wrote: > On 01/10/2013 06:17 AM, Tang Chen wrote: >>>> Note: if the memory provided by the memory device is used by the >>>> kernel, it >>>> can't be offlined. It is not a bug. >>> >>> Right. But how often does this happen in testing? In other words, >>> please provide an overall description of how well memory hot-remove is >>> presently operating. Is it reliable? What is the success rate in >>> real-world situations? >> >> We test the hot-remove functionality mostly with movable_online used. >> And the memory used by kernel is not allowed to be removed. > > Can you try doing this using cpusets configured to hardwall ? > It is my understanding that the object allocators will try hard not to > allocate anything outside the walls defined by cpuset. Which means that > if you have one process per node, and they are hardwalled, your kernel > memory will be spread evenly among the machine. With a big enough load, > they should eventually be present in all blocks. > I'm sorry I couldn't catch your point. Do you want to confirm whether cpuset can work enough instead of ZONE_MOVABLE ? Or Do you want to confirm whether ZONE_MOVABLE will not work if it's used with cpuset ? > Another question I have for you: Have you considering calling > shrink_slab to try to deplete the caches and therefore free at least > slab memory in the nodes that can't be offlined? Is it relevant? > At this stage, we don't consider to call shrink_slab(). We require nearly 100% success at offlining memory for removing DIMM. It's my understanding. IMHO, I don't think shrink_slab() can kill all objects in a node even if they are some caches. We need more study for doing that. Thanks, -Kame