From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59561) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtDhd-0001W3-AP for qemu-devel@nongnu.org; Mon, 02 Nov 2015 06:55:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtDhZ-0000lR-2b for qemu-devel@nongnu.org; Mon, 02 Nov 2015 06:55:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59987) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtDhY-0000l8-TL for qemu-devel@nongnu.org; Mon, 02 Nov 2015 06:55:04 -0500 References: <1446449823-25049-1-git-send-email-liang.z.li@intel.com> From: Paolo Bonzini Message-ID: <56374F11.30309@redhat.com> Date: Mon, 2 Nov 2015 12:54:57 +0100 MIME-Version: 1.0 In-Reply-To: <1446449823-25049-1-git-send-email-liang.z.li@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [v2 RESEND 0/4] Fix long vm downtime during live migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Liang Li , qemu-devel@nongnu.org Cc: amit.shah@redhat.com, Wanpeng Li , yong.y.wang@intel.com, stefanha@redhat.com, quintela@redhat.com On 02/11/2015 08:36, Liang Li wrote: > The patch 3ea3b7fa9af067982f34b of kvm introduces a lazy collapsing > of small sptes into large sptes mechanism, which intend to solve the > performance drop issue if live migration fails or is canceled. The > rmap will be scanned in the KVM_SET_USER_MEMORY_REGION ioctl context > when dirty logging is stopped so as to drop the small sptes, scanning > the rmap and drop the small sptes is a time consuming operation which > will take dozens of milliseconds, the actual time depends on VM's > memory size. For a VM with 8GB RAM, it will take about 30ms. I'm okay with these patches. Juan, can they be included in 2.5? However, the KVM patch is a regression too. Wanpeng, can you look into doing the collapsing from a work item? Thanks, Paolo