From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47528) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XhanE-0004BA-6V for qemu-devel@nongnu.org; Fri, 24 Oct 2014 05:04:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xhan9-0004Lw-FN for qemu-devel@nongnu.org; Fri, 24 Oct 2014 05:04:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58911) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xhan9-0004Lq-7s for qemu-devel@nongnu.org; Fri, 24 Oct 2014 05:04:15 -0400 Date: Fri, 24 Oct 2014 10:04:06 +0100 From: Stefan Hajnoczi Message-ID: <20141024090406.GA32480@stefanha-thinkpad.redhat.com> References: <391d6bb1-e0ad-49ea-afdc-fff462081f24@mailpro> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="7JfCtLOvnd9MIVvH" Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] is it possible to use a disk with multiple iothreads ? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexandre DERUMIER Cc: josh.durgin@inktank.com, qemu-devel --7JfCtLOvnd9MIVvH Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Oct 23, 2014 at 08:26:17PM +0200, Alexandre DERUMIER wrote: > I was reading this interesting presentation,=20 >=20 > http://vmsplice.net/~stefan/stefanha-kvm-forum-2014.pdf=20 >=20 > and I have a specific question. >=20 >=20 > I'm currently evaluate ceph/rbd storage performance through qemu, >=20 > and the current bottleneck seem to be the cpu usage of the iothread. > (rbd procotol cpu usage is really huge). >=20 > Currently It's around 10000iops on 1core of recent xeons. >=20 >=20 >=20 > So, I had tried with virtio-scsi multiqueue, but it doesn't help. (Not su= re, but I think that all queues are mapped on 1 iothread ?) >=20 > I had tried with with virtio-blk and iothread/dataplane, it's help a litt= le , but not too much too. >=20 > So, my question is : Is it possible to use multiple iothreads with 1 disk= ? >=20 > (something like 1 queue - 1 iothread?) virtio-blk and virtio-scsi emulation only runs in 1 thread at a time. It is currently not possible to achieve true multiqueue from guest, through QEMU, and down to the host. This is what the final slides in my presentation were about. Regarding Ceph, do you know why it burns a lot of CPU? CCed Josh in case he has ideas for reducing Ceph library CPU utilization. Stefan --7JfCtLOvnd9MIVvH Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJUShYFAAoJEJykq7OBq3PIVPkH/0YmxGNoET0R/TWahGUZxuPX q1UgW18MdVn/mlfNqimdbYImVwrsOoXQe3th2V0Wg9rvR3pqFvwFey8N5BhOFkcX lgwdeIbpD15wBp5pSu+sswhuavQwGVXmG9ZaQVnINAm/EcQaxbabko8NnsCR9jTa 3LbYIe+w+FRg3IVP/gFU6jr3SkQTbptwiNAjfN3vU59PMzDeF2/8kIX7EAhbAXZ3 tsUaSLw2pilP76VUYpN9mQxrKXZi+/5qY2IBiUYGcr5pH1pjdis2f/vp8oXuiNJC k0RZF8fee1oT6rFA3tC5lNcEWKuCNriBvUHQrB+bR9oVGFGYfW6PhIrXsTTfuQo= =kG0G -----END PGP SIGNATURE----- --7JfCtLOvnd9MIVvH--