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.
> >
> > 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.
>
> 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 \
'Options[_]: bits,growright' xxxxxxxxxxxxxx@xxxxxxxxx
[...]
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
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