From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758636AbcLOPeh (ORCPT ); Thu, 15 Dec 2016 10:34:37 -0500 Received: from mga07.intel.com ([134.134.136.100]:3101 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755813AbcLOPef (ORCPT ); Thu, 15 Dec 2016 10:34:35 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,352,1477983600"; d="scan'208";a="42969450" Subject: Re: [Qemu-devel] [PATCH kernel v5 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration To: "Li, Liang Z" , Andrea Arcangeli References: <1480495397-23225-1-git-send-email-liang.z.li@intel.com> <0b18c636-ee67-cbb4-1ba3-81a06150db76@redhat.com> <0b83db29-ebad-2a70-8d61-756d33e33a48@intel.com> <2171e091-46ee-decd-7348-772555d3a5e3@redhat.com> <20161207183817.GE28786@redhat.com> <20161207202824.GH28786@redhat.com> <060287c7-d1af-45d5-70ea-ad35d4bbeb84@intel.com> Cc: David Hildenbrand , "kvm@vger.kernel.org" , "mhocko@suse.com" , "mst@redhat.com" , "linux-kernel@vger.kernel.org" , "qemu-devel@nongnu.org" , "linux-mm@kvack.org" , "dgilbert@redhat.com" , "pbonzini@redhat.com" , "akpm@linux-foundation.org" , "virtualization@lists.linux-foundation.org" , "kirill.shutemov@linux.intel.com" From: Dave Hansen Message-ID: <01886693-c73e-3696-860b-086417d695e1@intel.com> Date: Thu, 15 Dec 2016 07:34:33 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: 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 12/14/2016 12:59 AM, Li, Liang Z wrote: >> Subject: Re: [Qemu-devel] [PATCH kernel v5 0/5] Extend virtio-balloon for >> fast (de)inflating & fast live migration >> >> On 12/08/2016 08:45 PM, Li, Liang Z wrote: >>> What's the conclusion of your discussion? It seems you want some >>> statistic before deciding whether to ripping the bitmap from the ABI, >>> am I right? >> >> I think Andrea and David feel pretty strongly that we should remove the >> bitmap, unless we have some data to support keeping it. I don't feel as >> strongly about it, but I think their critique of it is pretty valid. I think the >> consensus is that the bitmap needs to go. >> >> The only real question IMNHO is whether we should do a power-of-2 or a >> length. But, if we have 12 bits, then the argument for doing length is pretty >> strong. We don't need anywhere near 12 bits if doing power-of-2. > > Just found the MAX_ORDER should be limited to 12 if use length instead of order, > If the MAX_ORDER is configured to a value bigger than 12, it will make things more > complex to handle this case. > > If use order, we need to break a large memory range whose length is not the power of 2 into several > small ranges, it also make the code complex. I can't imagine it makes the code that much more complex. It adds a for loop. Right? > It seems we leave too many bit for the pfn, and the bits leave for length is not enough, > How about keep 45 bits for the pfn and 19 bits for length, 45 bits for pfn can cover 57 bits > physical address, that should be enough in the near feature. > > What's your opinion? I still think 'order' makes a lot of sense. But, as you say, 57 bits is enough for x86 for a while. Other architectures.... who knows?