From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44597) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UuM8i-0006Vd-OA for qemu-devel@nongnu.org; Wed, 03 Jul 2013 08:26:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UuM8d-00034S-3y for qemu-devel@nongnu.org; Wed, 03 Jul 2013 08:26:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:4666) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UuM8c-00033i-QL for qemu-devel@nongnu.org; Wed, 03 Jul 2013 08:26:22 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r63CQLDc018826 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 3 Jul 2013 08:26:21 -0400 Date: Wed, 3 Jul 2013 14:26:20 +0200 From: Stefan Hajnoczi Message-ID: <20130703122620.GA19455@stefanha-thinkpad.muc.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [Qemu-devel] Dataplane status for RHEL7 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Paolo Bonzini , areis@redhat.com Ademar asked for a status update on virtio-blk-data-plane. Here is my status, please let me know if you have any questions or concerns. RHEL7 Features -------------- For RHEL7 my goal is to deliver the following dataplane features: 1. Image format support 2. QMP 'transaction' support (creating backing file snapshots at runtime) 3. QMP 'block_resize' support 4. I/O throttling support 1-3 have been posted in an RFC series to qemu-devel. I will send out patch series at the end of this week for QEMU 1.6. This will also include patches for 4. I'd like to ask IBM to help in the performance evaluation. We must compare against the upstream dataplane code, which bypasses the block layer. It would be bad if the new dataplane with the block layer is significantly slower :). Backport -------- Since RHEL7 is based on QEMU 1.5.x the backport should be reasonable. I don't foresee any particular challenge since the delta against upstream will be small. This backport should still happen during the RHEL7 Development Phase (ending 2013/08/14) since QEMU 1.6 release is 2013/08/15 and the patches must be upstream before that. RHEL7.1 Features ---------------- What remains to be done after QEMU 1.6 (RHEL 7.1?): 1. Block jobs 2. NBD exports The solution for 1 & 2 is to run the code in the dataplane thread. 3. Hot unplug This requires revisiting our crude bdrv_in_use() mechanism, perhaps to protect against any remaining commands that would interfere with dataplane. 4. Live migration We lack something like vhost log for dataplane. The dataplane thread must be able to queue dirty memory areas (accessed by I/O and vring processing) so that live migration does not miss pages that were modified in the dataplane thread. Stefan