From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f43.google.com (mail-pb0-f43.google.com [209.85.160.43]) by kanga.kvack.org (Postfix) with ESMTP id 61F0D6B0031 for ; Wed, 9 Oct 2013 17:46:00 -0400 (EDT) Received: by mail-pb0-f43.google.com with SMTP id md4so1515107pbc.30 for ; Wed, 09 Oct 2013 14:46:00 -0700 (PDT) Received: by mail-pa0-f52.google.com with SMTP id kl14so1704173pab.11 for ; Wed, 09 Oct 2013 14:45:57 -0700 (PDT) Message-ID: <5255CE7D.8030007@gmail.com> Date: Thu, 10 Oct 2013 05:45:33 +0800 From: Zhang Yanfei MIME-Version: 1.0 Subject: Re: [PATCH part1 v6 4/6] x86/mem-hotplug: Support initialize page tables in bottom-up References: <524E2032.4020106@gmail.com> <524E2127.4090904@gmail.com> <5251F9AB.6000203@zytor.com> <525442A4.9060709@gmail.com> <20131009164449.GG22495@htj.dyndns.org> <52558EEF.4050009@gmail.com> <20131009192040.GA5592@mtj.dyndns.org> <1381352311.5429.115.camel@misato.fc.hp.com> <20131009211136.GH5592@mtj.dyndns.org> <5255C730.90602@zytor.com> In-Reply-To: <5255C730.90602@zytor.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "H. Peter Anvin" Cc: Tejun Heo , Toshi Kani , Andrew Morton , "Rafael J . Wysocki" , lenb@kernel.org, Thomas Gleixner , mingo@elte.hu, Wanpeng Li , Thomas Renninger , Yinghai Lu , Jiang Liu , Wen Congyang , Lai Jiangshan , isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, Mel Gorman , Minchan Kim , mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, Rik van Riel , jweiner@redhat.com, prarit@redhat.com, "x86@kernel.org" , linux-doc@vger.kernel.org, "linux-kernel@vger.kernel.org" , Linux MM , linux-acpi@vger.kernel.org, imtangchen@gmail.com, Zhang Yanfei , Tang Chen Hello Peter, On 10/10/2013 05:14 AM, H. Peter Anvin wrote: > On 10/09/2013 02:11 PM, Tejun Heo wrote: >> Hello, Toshi. >> >> On Wed, Oct 09, 2013 at 02:58:31PM -0600, Toshi Kani wrote: >>> Let's not assume that memory hotplug is always a niche feature for huge >>> & special systems. It may be a niche to begin with, but it could be >>> supported on VMs, which allows anyone to use. Vasilis has been working >>> on KVM to support memory hotplug. >> >> I'm not saying hotplug will always be niche. I'm saying the approach >> we're currently taking is. It seems fairly inflexible to hang the >> whole thing on NUMA nodes. What does the planned kvm support do? >> Splitting SRAT nodes so that it can do both actual NUMA node >> distribution and hotplug granuliarity? IIRC I asked a couple times >> what the long term plan was for this feature and there doesn't seem to >> be any road map for this thing to become a full solution. Unless I >> misunderstood, this is more of "let's put out the fire as there >> already are (or gonna be) machines which can do it" kinda thing, which >> is fine too. My point is that it doesn't make a lot of sense to >> change boot sequence invasively to accomodate that. >> > > I would also argue that in the VM scenario -- and arguable even in the > hardware scenario -- the right thing is to not expose the flexible > memory in the e820/EFI tables, and instead have it hotadded (possibly > *immediately* so) on boot. This avoids both the boot time funnies as > well as the scaling issues with metadata. > So in this kind of scenario, hotpluggable memory will not be detected at boot time, and admin should not use this movable_node boot option and the kernel will act as before, using top-down allocation always. -- Thanks. Zhang Yanfei -- 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