Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932885AbcCIOTW (ORCPT ); Wed, 9 Mar 2016 09:19:22 -0500 Received: from mga11.intel.com ([192.55.52.93]:2734 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932869AbcCIOTO convert rfc822-to-8bit (ORCPT ); Wed, 9 Mar 2016 09:19:14 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,311,1455004800"; d="scan'208";a="760953988" From: "Li, Liang Z" To: Roman Kagan , "Dr. David Alan Gilbert" CC: Paolo Bonzini , "ehabkost@redhat.com" , "kvm@vger.kernel.org" , "mst@redhat.com" , "quintela@redhat.com" , "linux-kernel@vger.kernel.org" , "qemu-devel@nongnu.org" , "linux-mm@kvack.org" , "amit.shah@redhat.com" , "akpm@linux-foundation.org" , "virtualization@lists.linux-foundation.org" , "rth@twiddle.net" Subject: RE: [Qemu-devel] [RFC qemu 0/4] A PV solution for live migration optimization Thread-Topic: [Qemu-devel] [RFC qemu 0/4] A PV solution for live migration optimization Thread-Index: AQHRdTqPjTxTnYWKZEWM4lf/HjT6rZ9HeJiAgAEJK0D//+lWAIAAiTOQ//+bAoCAAMUSUP//n7sAAAUgY4AA7/YKgAASehjA Date: Wed, 9 Mar 2016 14:19:04 +0000 Message-ID: References: <1457001868-15949-1-git-send-email-liang.z.li@intel.com> <20160303174615.GF2115@work-vm> <20160304081411.GD9100@rkaganb.sw.ru> <20160304102346.GB2479@rkaganb.sw.ru> <56D9B6C2.3070708@redhat.com> <20160304185120.GB2588@work-vm> <20160309132210.GA5869@rkaganb.sw.ru> In-Reply-To: <20160309132210.GA5869@rkaganb.sw.ru> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiMzEzOTI0NzgtYWU2Yi00NzU4LTlmMzQtMWMxMzdkZGE0NGEzIiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX0lDIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE1LjkuNi42IiwiVHJ1c3RlZExhYmVsSGFzaCI6InhjMkVnWWllZkIwSDBqUFZQUXU1RERYc1pqVlhqendQMDcyYVExb01ENkU9In0= x-ctpclassification: CTP_IC x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2135 Lines: 49 > On Fri, Mar 04, 2016 at 06:51:21PM +0000, Dr. David Alan Gilbert wrote: > > * Paolo Bonzini (pbonzini@redhat.com) wrote: > > > > > > > > > On 04/03/2016 15:26, Li, Liang Z wrote: > > > >> > > > > >> > The memory usage will keep increasing due to ever growing > > > >> > caches, etc, so you'll be left with very little free memory fairly soon. > > > >> > > > > > I don't think so. > > > > > > > > > > Roman is right. For example, here I am looking at a 64 GB > > > (physical) machine which was booted about 30 minutes ago, and which > > > is running disk-heavy workloads (installing VMs). > > > > > > Since I have started writing this email (2 minutes?), the amount of > > > free memory has already gone down from 37 GB to 33 GB. I expect > > > that by the time I have finished running the workload, in two hours, > > > it will not have any free memory. > > > > But what about a VM sitting idle, or that just has more RAM assigned > > to it than is currently using. > > I've got a host here that's been up for 46 days and has been doing > > some heavy VM debugging a few days ago, but today: > > > > # free -m > > total used free shared buff/cache available > > Mem: 96536 1146 44834 184 50555 94735 > > > > I very rarely use all it's RAM, so it's got a big chunk of free RAM, > > and yes it's got a big chunk of cache as well. > > One of the promises of virtualization is better resource utilization. > People tend to avoid purchasing VMs so much oversized that they never > touch a significant amount of their RAM. (Well, at least this is how things > stand in hosting market; I guess enterprize market is similar in this regard). > > That said, I'm not at all opposed to optimizing the migration of free memory; > what I'm trying to say is that creating brand new infrastructure specifically for > that case doesn't look justified when the existing one can cover it in addition > to much more common scenarios. > > Roman. Even the existing one can cover more common scenarios, but it has performance issue. that's why I create a new one. Liang