From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43705) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIS5t-0005CF-VR for qemu-devel@nongnu.org; Wed, 20 Mar 2013 19:06:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UIS5q-0006qf-DZ for qemu-devel@nongnu.org; Wed, 20 Mar 2013 19:06:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35018) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIS5q-0006qT-6L for qemu-devel@nongnu.org; Wed, 20 Mar 2013 19:06:50 -0400 Message-ID: <514A4104.9000505@redhat.com> Date: Wed, 20 Mar 2013 17:06:44 -0600 From: Eric Blake MIME-Version: 1.0 References: <20130320081130.GA5953@stefanha-thinkpad.muc.redhat.com> In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="----enig2FTFNKVSPSWMWDJKGTNXQ" Subject: Re: [Qemu-devel] kvm suspend performance List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Knauth Cc: Stefan Hajnoczi , qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) ------enig2FTFNKVSPSWMWDJKGTNXQ Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 03/20/2013 04:44 PM, Thomas Knauth wrote: > Hi Stefan, >=20 > thanks for taking the time to reply. >=20 > On Wed, Mar 20, 2013 at 9:11 AM, Stefan Hajnoczi w= rote: >=20 >> Which QEMU or libvirt command are you using to suspend the guest to >> disk? >> >=20 > virsh save Then this is as much a libvirt question as a qemu question. Which version of libvirt? 'virsh save' maps to the qemu 'migrate' monitor command, with a destination of migration to file. On older libvirt, we just relied on qemu's default throttling during migration. Remember, qemu throttles migration by default, so that it is less likely to saturate a network link; but while this makes sense for a migration to a remote network location, it gets in the way of a migration to a local fil= e. In newer libvirt, we added code so that when migrating to a file, we temporarily raise the qemu throttling to be effectively unlimited. In my own testing, it provided nearly a 10x speedup on the time for 'virsh save' on the guests that I was testing on my own machine. Meanwhile, if your libvirt is too old to have the automatic temporary change to the throttling limit, you should be able to issue 'virsh migrate-setspeed $dom 1000000' (or some other large number), to raise the qemu throttling limits to a much higher rate of MiB/s permitted during the migration to file. > Which versions of libvirt and QEMU are you using? >=20 >=20 > I've tried this on a couple of machines with differing versions of Ubun= tu > (12.04, 10.10, and 10.04). They are all showing the same performance. T= he > machine where I did most of my measurements was the 12.04 machine. The > versions are libvirt 0.9.8-2ubuntu17 and > qemu-kvm 1.0+noroms-0ubuntu14.7. That explains it. Libvirt migration-to-file with unlimited speed wasn't until upstream commit v0.10.0-rc0-62-g6cfdeaa. I really wish the Ubuntu distro would quit shipping what feels like stone-age libvirt. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org ------enig2FTFNKVSPSWMWDJKGTNXQ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJRSkEEAAoJEKeha0olJ0NqMegH/1yW/XmY/R5pN0DwBuGvXQRE Sm6EydokR+alrvWNY+LQf8oHgYFioyJ8wiTZ5pa+rgP/Ewn5eE4X3ZCkFxcKCw9l gE1Se1F3HGbCZpM8pO784HimAHSDj6B0yRms0KJglNnmmingIBxfu0bZm31XJfz+ h6G2Ea5115CnadWgakZWKiCSooUf5bxCI2/Ycd4oE7RUXkWNvsnGCp01tdLkwulY kCQ5mJOGIx7J8jbgM0q/9P/YdBJe4+GpDdla/Rk3FbcSoUDzRFIaI/2Pn/G9SySB 5FEdhXKpstfLOL5CpTNtQddpwinLYqxt7oEBeADbGcA3ihpRmDyKQNrbjbfmeJQ= =otF4 -----END PGP SIGNATURE----- ------enig2FTFNKVSPSWMWDJKGTNXQ--