[libvirt-users] getting oriented/networking [some success]

Boylan, Ross Ross.Boylan at ucsf.edu
Mon Mar 23 18:44:22 UTC 2015

After "ethtool -K eth0 gro off" ssh into the machine (either the host or the VM's) became unreliable--very slow, with frequent dropped connections.  However, this was while using sshuttle.
From: Boylan, Ross
Sent: Friday, March 20, 2015 1:12 PM
To: libvirt-users at redhat.com
Subject: RE: [libvirt-users] getting oriented/networking [some success]

I seem to have run into https://bugzilla.redhat.com/show_bug.cgi?id=855640, because when I tried the fix/work-around at the end (comment 11), ethtool -K eth0 gro off, my download speed by speedtest went from undetectable to ~150Mb/s.  However, it was not able to connect for the upload test, and so something may still be off.  Non-virtual machines can do the upload test, so it's not just a firewall issue.

The comment refers to another source for more info, but it seems to be behind a Redhat paywall.

From: Boylan, Ross
Sent: Friday, March 20, 2015 11:01 AM
To: Dominique Ramaekers; libvirt-users at redhat.com
Subject: RE: [libvirt-users] getting oriented/networking

Thanks very much.  Unfortunately, networking is currently so slow as to be non-functional (most operations time out).  It's also erratic: I had 2 VM that were close to identical--they were both based on the same disk image--and even when I set the networking the same one was fine and one was very slow.  Today I started up the VM that had good networking, and it now has bad networking.

Here's one of the network specifications:
    <interface type='direct'>
      <mac address='52:54:00:61:7c:dc'/>
      <source dev='eth1' mode='vepa'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
The one that was originally fast also had a NAT network, and the one that was originally slow was mode bridge before I changed it to vepa, which didn't help.

The drivers came from http://alt.fedoraproject.org/pub/alt/virtio-win/latest/images/virtio-win-0.1-100.iso in the 32 bit windows 7 directory of the iso (host is 64 bit, as is the emulated machine; Windows 7 is 32 bit).  I've tried shutting down, removing and reinstalling the network adaptor, and various other things.
From: Dominique Ramaekers [dominique.ramaekers at cometal.be]
Sent: Thursday, March 19, 2015 11:21 PM
To: Boylan, Ross; libvirt-users at redhat.com
Subject: RE: [libvirt-users] getting oriented/networking

Dear Boyland,

In collaboration with some of this mailing list users, I had put some effort in optimising the guest settings in function of a windows guest. The libvirt-gui doesn't include these options. You'll have to edit the XML in virsh. This was my conclusion on 15-03-2015 but I added the hugepages tip in this list today. As for networking, I only use or bridged or the default virtual network (NAT), so can't help you more here.

Here below, a summary of tips:
- Setting video to QXL and the display channel to Spice
                 <model type='qxl' ram='65536' vram='65536' heads='1'/>
                <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
        <channel type='spicevmc'>
                <target type='virtio' name='com.redhat.spice.0'/>
                <address type='virtio-serial' controller='0' bus='0' port='1'/>
- Using HyperV enlightenemt timer
                        <relaxed state='on'/>
                        <vapic state='on'/>
                        <spinlocks state='on' retries='8191'/>
        <clock ...>
                <timer name='hypervclock' present='yes'/>
- Delete the tablet entry in the input section or set the USB-bus to USB2 or USB3
- Use hugepages

Again thanks Daniel and Andrey.

Hope this helps.

Grts, Dominique.

-----Oorspronkelijk bericht-----
Van: Boylan, Ross [mailto:Ross.Boylan at ucsf.edu]
Verzonden: vrijdag 20 maart 2015 1:52
Aan: libvirt-users at redhat.com
Onderwerp: [libvirt-users] getting oriented/networking

I've been using virt-manager and kvm with a disk image (as in the raw bits) from a physical windows 7 machine.  Initial performance was dreadful, but improved as I switched to virtio and spice.  I've been running linux VM's somewhat longer (much longer if you count kvm without libvirt).

There are lots of choices exposed by virt-manager.  How do I find out what the choices mean, and which are good ones?  This was true for the video (resolved by following instructions for spice, though I still wonder what the other settings are for), disks and the network.

In particular, I have a choice of lots of interfaces for my network; I picked eth1:macvtap because I wanted to bridge eth1.  But there is a "Source Mode" which I left at VEPA, even though Bridged was another choice.  But the bridge would already seem implicit in picking a source device of eth1:macvtap.  I don't know what "source mode" means.  The choices in the GUI seem like some of the options listed under forward on http://libvirt.org/formatnetwork.html; is that a good place to look for clarification.

I started a 2nd VM that also used eth1:macvtap (with virtio) and it had almost no network throughput.  So maybe I should use some other method?  I notice the network manager connection gui allows creation of bridges on the network; should I be using that?

I have been reading documentation, but I haven't found either a task-oriented discussion ("to get a windows machine working well, use these options" or "follow these steps") or an easy way to go from the choices in the GUI to a discussion of their meaning.

Thanks for any help you can offer.
Ross Boylan

libvirt-users mailing list
libvirt-users at redhat.com

More information about the libvirt-users mailing list