libvirt users - Feb 2016 - Network speed between two guests on same host.

Hi,

I've got two hosts. Most of my guests are Windows systems. I'm using
LANBench to test network performance.

1) From an physical PC to a guest (it doesn't matter on which host), I get
almost 1Gb/s. They are connected through a 1Gb/s swich => very good!

2) From a guest on one host to a guest on the other host => plusminus 1Gb/s
=> Okay!

3) Between two guests on the same host => plusminus 230Mb/s ???

The guests have network over a bridged interface, so I tried the same test over
a NAT interface => The same 230Mb/s...

Is there a way to tweak connection speeds between two guest running on the same
host?

Thanks in advance...

An piece of the xml dump of one of the guests:
<domain type='kvm' id='17'>
  <name>PCVIRTdra</name>
  <uuid>925e4f9b-2c27-406d-bdd9-f3e0b44f28bb</uuid>
  <title>PCVIRTdra - PC voor dra</title>
  <description></description>
  <memory unit='KiB'>2097152</memory>
  <currentMemory unit='KiB'>2097152</currentMemory>
  <memoryBacking>
    <hugepages/>
  </memoryBacking>
  <vcpu placement='static'>8</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64'
machine='pc-i440fx-utopic'>hvm</type>
    <bootmenu enable='yes'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv>
      <relaxed state='on'/>
      <vapic state='on'/>
      <spinlocks state='on' retries='8191'/>
    </hyperv>
  </features>
  <cpu mode='custom' match='exact'>
    <model fallback='allow'>cpu64-rhel6</model>
    <topology sockets='2' cores='2' threads='2'/>
  </cpu>
  <clock offset='localtime'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
    <timer name='hypervclock' present='yes'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <pm>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
  </pm>
  <devices>
    ....
    <interface type='bridge'>
      <mac address='52:54:00:b1:41:b3'/>
      <source bridge='br0'/>
      <target dev='vnet4'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x03' function='0x0'/>
    </interface>
.....

Have a look if vhost_net is loaded on the guest and if not load it with
modeprobe vhost_net

Last when doing your lab perf test are you sure that you are not penalised by
disk io either in input or outputs

Envoyé de mon iPhone
> Le 29 févr. 2016 à 17:13, Dominique Ramaekers
<dominique.ramaekers@cometal.be> a écrit :
> 
> Hi,
> 
> I've got two hosts. Most of my guests are Windows systems. I'm
using LANBench to test network performance.
> 
> 1) From an physical PC to a guest (it doesn't matter on which host), I
get almost 1Gb/s. They are connected through a 1Gb/s swich => very good!
> 
> 2) From a guest on one host to a guest on the other host => plusminus
1Gb/s => Okay!
> 
> 3) Between two guests on the same host => plusminus 230Mb/s ???
> 
> The guests have network over a bridged interface, so I tried the same test
over a NAT interface => The same 230Mb/s...
> 
> Is there a way to tweak connection speeds between two guest running on the
same host?
> 
> Thanks in advance...
> 
> An piece of the xml dump of one of the guests:
> <domain type='kvm' id='17'>
>  <name>PCVIRTdra</name>
>  <uuid>925e4f9b-2c27-406d-bdd9-f3e0b44f28bb</uuid>
>  <title>PCVIRTdra - PC voor dra</title>
>  <description></description>
>  <memory unit='KiB'>2097152</memory>
>  <currentMemory unit='KiB'>2097152</currentMemory>
>  <memoryBacking>
>    <hugepages/>
>  </memoryBacking>
>  <vcpu placement='static'>8</vcpu>
>  <resource>
>    <partition>/machine</partition>
>  </resource>
>  <os>
>    <type arch='x86_64'
machine='pc-i440fx-utopic'>hvm</type>
>    <bootmenu enable='yes'/>
>  </os>
>  <features>
>    <acpi/>
>    <apic/>
>    <hyperv>
>      <relaxed state='on'/>
>      <vapic state='on'/>
>      <spinlocks state='on' retries='8191'/>
>    </hyperv>
>  </features>
>  <cpu mode='custom' match='exact'>
>    <model fallback='allow'>cpu64-rhel6</model>
>    <topology sockets='2' cores='2'
threads='2'/>
>  </cpu>
>  <clock offset='localtime'>
>    <timer name='rtc' tickpolicy='catchup'/>
>    <timer name='pit' tickpolicy='delay'/>
>    <timer name='hpet' present='no'/>
>    <timer name='hypervclock' present='yes'/>
>  </clock>
>  <on_poweroff>destroy</on_poweroff>
>  <on_reboot>restart</on_reboot>
>  <on_crash>restart</on_crash>
>  <pm>
>    <suspend-to-mem enabled='no'/>
>    <suspend-to-disk enabled='no'/>
>  </pm>
>  <devices>
>    ....
>    <interface type='bridge'>
>      <mac address='52:54:00:b1:41:b3'/>
>      <source bridge='br0'/>
>      <target dev='vnet4'/>
>      <model type='virtio'/>
>      <alias name='net0'/>
>      <address type='pci' domain='0x0000'
bus='0x00' slot='0x03' function='0x0'/>
>    </interface>
> .....
> 
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