From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Bareiro Subject: Re: Bandwith limitation with KVM VMs Date: Mon, 3 Aug 2009 22:17:42 -0300 Message-ID: <20090804011742.GL23503@defiant.freesoftware.org> References: <20090803163205.GJ23503@defiant.freesoftware.org> <4A7715CC.7030901@gmail.com> Reply-To: dbareiro@gmx.net Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="Bzq2cJcN05fcPrs+" To: KVM General Return-path: Received: from mail.gmx.net ([213.165.64.20]:37011 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753890AbZHDBRr (ORCPT ); Mon, 3 Aug 2009 21:17:47 -0400 Received: from defiant (defiant.freesoftware.org [10.1.0.65]) by hermes.freesoftware.org (Postfix) with ESMTP id 2721B9C9 for ; Mon, 3 Aug 2009 22:17:39 -0300 (ART) Content-Disposition: inline In-Reply-To: <4A7715CC.7030901@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: --Bzq2cJcN05fcPrs+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Gregory. On Monday, 03 August 2009 12:52:28 -0400, Gregory Haskins wrote: > > I have a KVM VM that it has installed a MRTG on the network > > interface and that it doesn't register more than 10 Mbps, seeming > > that per moments it is saturated in this value. > >=20 > > Has KVM some bandwidth limitation of the virtualized network > > interfaces? In such case, exists some way to increase that > > limitation? > There is no set artificial limit afaict, though there are a large > number of factors that can affect performance. Of course, everything > has an ultimate ceiling (KVM included) but I have found this limit in > KVM to be orders of magnitude faster than 10Mbps. Properly tuned, > you should easily be able to saturate a GE link at line rate, or even > 4Gbps-5Gpbs of a 10GE link. > However, since you are only hitting 10Mb/s now, there is ton of > headroom left even on upstream KVM so you might find it to be > satisfactory as is, once you address the current bottleneck in your > setup. >=20 > Things to check: What linkspeed does the host see to the next hop? > How much bandwidth does the host see to the same end-point? What is > your overall topology, especially for the VM (are you using -net tap, > etc). What MTU are you using. Etc. It draws attention that when executing 'cfgmaker' from MRTG server against the IP of the VM, it returns max speed of 1250 kBytes/s, that is to say 10 Mbps: sparky:~# /usr/bin/cfgmaker --global 'WorkDir: /tmp' --global \=20 'Options[_]: bits,growright' xxxxxxxxxxxxxx@10.1.0.42 [...] MaxBytes[10.1.0.42_2]: 1250000 But nevertheless from within of the VM I see the following thing: aps2:~# ethtool eth0 Settings for eth0: Supported ports: [ TP MII ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full Advertised auto-negotiation: Yes Speed: 100Mb/s Duplex: Full Port: MII PHYAD: 32 Transceiver: internal Auto-negotiation: on Supports Wake-on: pumbg Wake-on: d Current message level: 0x00000007 (7) Link detected: yes do you think that can give some indication? Thanks for your reply. Regards, Daniel --=20 Fingerprint: BFB3 08D6 B4D1 31B2 72B9 29CE 6696 BF1B 14E6 1D37 Powered by Debian GNU/Linux Squeeze - Linux user #188.598 --Bzq2cJcN05fcPrs+ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkp3jDYACgkQZpa/GxTmHTfk3gCeMQK2wzAyk0pdYWAq1pSZr6v1 aT8AnisbJk5tE0r52DKrJ29jffYMk+wI =sABz -----END PGP SIGNATURE----- --Bzq2cJcN05fcPrs+--