From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id 7B02F6B0038 for ; Thu, 13 Apr 2017 22:26:54 -0400 (EDT) Received: by mail-io0-f198.google.com with SMTP id h72so64042119iod.0 for ; Thu, 13 Apr 2017 19:26:54 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTPS id n129si1047666itd.2.2017.04.13.19.26.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Apr 2017 19:26:53 -0700 (PDT) Message-ID: <58F033D0.7080101@intel.com> Date: Fri, 14 Apr 2017 10:28:32 +0800 From: Wei Wang MIME-Version: 1.0 Subject: Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration References: <1492076108-117229-1-git-send-email-wei.w.wang@intel.com> <20170413204411.GJ784@bombadil.infradead.org> <20170414044515-mutt-send-email-mst@kernel.org> In-Reply-To: <20170414044515-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Michael S. Tsirkin" , Matthew Wilcox Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, david@redhat.com, dave.hansen@intel.com, cornelia.huck@de.ibm.com, akpm@linux-foundation.org, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, liliang.opensource@gmail.com On 04/14/2017 09:50 AM, Michael S. Tsirkin wrote: > On Thu, Apr 13, 2017 at 01:44:11PM -0700, Matthew Wilcox wrote: >> On Thu, Apr 13, 2017 at 05:35:03PM +0800, Wei Wang wrote: >>> 2) transfer the guest unused pages to the host so that they >>> can be skipped to migrate in live migration. >> I don't understand this second bit. You leave the pages on the free list, >> and tell the host they're free. What's preventing somebody else from >> allocating them and using them for something? Is the guest semi-frozen >> at this point with just enough of it running to ask the balloon driver >> to do things? > There's missing documentation here. > > The way things actually work is host sends to guest > a request for unused pages and then write-protects all memory. > > So guest isn't frozen but any changes will be detected by host. > Probably it's better to say " transfer the info about the guest unused pages to the host so that the host gets a chance to skip the transfer of the unused pages during live migration". Best, Wei -- 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