[libvirt] [PATCH 0/7] Add support for setting QoS

[Laine Stump]

On 06/23/2011 11:36 AM, Michal Privoznik wrote:
> This patch series add support for setting traffic shaping and policing
> on both domain's interface and network's virtual bridge. Basically,
> this is done via 'tc' from iproute2 package. For shaping is HTB used,
> for policing we need u32 match selector. Both should be available in
> RHEL-6 kernel.

Some general questions:

1) Just to make sure I understand it, if <bandwidth> is specified in the 
network XML, that will be applied to the bridge itself, not to each 
interface on the bridge. (So, if we want to have the per-guest bandwidth 
specified in a single place, that will be where my proposed <portgroup> 
comes in - a <bandwidth> specified in a <portgroup> will be applied 
individually to each guest interface that is part of the portgroup.)

2) Following on (2). Once host bridges (ie, a bridge device that's 
directly connected to a physical NIC) are available as <network>s, can 
the limiting then be applied to the bridge device, or will it instead 
need to be applied to the ethernet device that the bridge is using to 
attach to the physical network? If the latter is the case, then we'll 
need a way to determine which device that is (currently I hadn't planned 
on putting that information in the XML, because it's configured outside 
of libvirt, and this could lead to mismatches between what libvirt XML 
shows and reality).

3) Similarly for macvtap <network>s, will the network-wide bandwidth 
limiting be applied to the physical ethernet device? This would have the 
side effect of including host traffic on that interface in the bandwidth 
totals, but I don't see a way around it.

4) Finally on that topic, what about <network>s that have a pool of 
physical ethernets to be used macvtap-style? Is there any way we can do 
bandwidth limiting on an aggregated collection of network interfaces? Or 
will attempts to configure this necessarily result in a "config not 
supported" log message?

5) I see you've put the data structures and parsing/formatting functions 
that are used by both network_conf.c and domain_conf.c in the util 
directory. I've been wondering myself what to do with similar 
structs/functions that will be used in both network and domain XML (eg, 
<virtualport> will soon be used by both) - does everyone agree this is 
the right way to handle it? Or should there be a common file in the conf 
directory instead? (I don't have an opinion, but want to "do the right 
thing" when I write my own code)