Hi Gregory.
On Monday, 03 August 2009 23:01:30 -0400,
Gregory Haskins wrote:
> >> 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?
> Hmm.. I am not familiar with MRTG/cfgmaker, but from your ethtool output
> I suspect you are not using virtio. How do you launch the guest?
The VMs are booted with a syntax similar to the following one:
root@ss02:~# ps ax|grep aps2|grep -v grep
28711 ? Sl 8171:06 kvm -hda /dev/vm/aps2-raiz -hdb \
/dev/vm/aps2-space -hdc /dev/vm/aps2-index -hdd /dev/vm/aps2-cache -m \
4096 -smp 4 -net nic,vlan=0,macaddr=00:16:3E:00:00:27 -net tap \
-daemonize -vnc :5 -k es -localtime -monitor \
telnet:localhost:4005,server,nowait -serial \
telnet:localhost:4045,server,nowait \
According to I was reading, it would be necessary to use with -net the
option model=virtio, so I would not be using virtio with the VMs.
In order to provide a little more information, I will say to you that
this VM is running on host with Ubuntu Hardy Heron server amd64 with
kernel 2.6.24 and kvm-62, both installed from the Ubuntu repositories,
but my idea is to upgrade in the short term to kernel 2.6.30 with KVM-88
compiled by myself basing me on a suggestion that did Avi to me by
problems that I am having of memory usage [1].
The host machine has two physical interfaces with the following
configuration:
auto br0
iface br0 inet static
address 10.1.0.47
netmask 255.255.0.0
network 10.1.0.0
broadcast 10.1.255.255
bridge_ports eth1
bridge_stp off
bridge_maxwait 5
auto eth0
iface eth0 inet static
address 10.3.0.47
netmask 255.255.0.0
network 10.3.0.0
broadcast 10.3.255.255
gateway 10.3.0.5
Executing ethtool from the host machine, I get the following data:
root@ss02:~# ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: g
Link detected: yes
root@ss02:~# ethtool eth1
Settings for eth1:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: g
Link detected: yes
Apparently even though the interface for bridge supports 10/100/1000,
the one of the VM is 10/100.
> Have you actually run something like netperf or an rsync to see what
> type of bandwidth you actually get? Perhaps this is just the mrtg
> tool getting confused about the actual interface capabilities.
It draws attention to me that I have MRTG registering the bandwidth of
several routers and for those cases it register over 10 Mbps without
problem. These are the values that I obtain in a snapshot with iptraf:
Iface Total IP NonIP BadIP Activity
lo 120 120 0 0 3,00 kbits/sec
eth0 2654 2654 0 0 56,40 kbits/sec
eth1 346250 346250 0 0 18459,20 kbits/sec
tap0 24 24 0 0 0,40 kbits/sec
tap2 128 128 0 0 1,20 kbits/sec
tap3 8366 8366 0 0 685,40 kbits/sec
tap1 24 24 0 0 0,40 kbits/sec
tap5 19531 19531 0 0 2742,80 kbits/sec
tap4 328258 328258 0 0 16127,80 kbits/sec
Also, according to MRTG, at this precise moment the VM interface is not
saturated in 10 Mbps. There is some command whose execution can be used
to associate a tap device with a VM?
Like additional note, I am observing that the sum of the activity on
each tap device exceeds the measurement for eth1. This can be possible?
Thanks for your reply.
Regards,
Daniel
[1] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/37704
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