From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: I/O performance of VirtIO Date: Tue, 13 Oct 2009 08:35:36 +0200 Message-ID: <4AD41FB8.6000209@web.de> References: <20091012204901.GA10688@nightfall.luchs.at> <4AD3A38D.3090102@msgid.tls.msk.ru> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig22AD230FA6462BFC1341B4F9" Cc: =?ISO-8859-1?Q?Ren=E9_Pfeiffer?= , kvm@vger.kernel.org To: Michael Tokarev Return-path: Received: from fmmailgate01.web.de ([217.72.192.221]:35091 "EHLO fmmailgate01.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755147AbZJMGgU (ORCPT ); Tue, 13 Oct 2009 02:36:20 -0400 In-Reply-To: <4AD3A38D.3090102@msgid.tls.msk.ru> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig22AD230FA6462BFC1341B4F9 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Michael Tokarev wrote: > Ren=E9 Pfeiffer wrote: >> Hello! >> >> I just tested qemu-kvm-0.11.0 with the KVM module of kernel 2.6.31.1. = I >> noticed that the I/O performance of an unattended stock Debian Lenny >> install dropped somehow. The test machines ran with kvm-88 and 2.6.30.= x >> before. The difference is very noticeable (went from about 5 minutes u= p >> to 15-25 minutes). The two test machines have different CPUs (one is a= n >> Intel Core2 CPU, the other runs with an AMD Athlon 64 X2 Dual). >> >> Is this the effect of added code regarding caching/data integrity to t= he >> VirtIO block layer or somewhere else? The qemu-system-x86_64 seems to >> hang a lot more in heavy I/O (showing 'D' in top/htop). >> >> The command line is quite straight-forward: >> qemu-system-x86_64 -drive file=3Ddebian.qcow2,if=3Dvirtio,boot=3Don -c= drom \ >> /srv/isos/debian-502-i386-netinst.iso -smp 2 -boot d -m 512 -net nic \= >> -net user -usb > ^^^^^^^^^ >=20 > Care to try with something more real than user-level networking? > You're using netinstall which - apparently - tries to use some > networking d/loading components etc, and userlevel networking is > known to be very very slow.... It can be particularly slow if you use in-kernel irqchips and the default NIC emulation (up to 10 times slower), some effect I always wanted to understand on a rainy day. So, when you actually want -net user, try -no-kvm-irqchip. Jan --------------enig22AD230FA6462BFC1341B4F9 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkrUH7wACgkQitSsb3rl5xR/lQCgxtz4v14y56yfJaW1J321eN52 GmIAn1sdCaBuAIVwNgvGyqggSAcSvQ4B =TXxb -----END PGP SIGNATURE----- --------------enig22AD230FA6462BFC1341B4F9--