Re: [Qemu-devel] Better qemu/kvm defaults (was Re: [RFC PATCH 0/4] Gang scheduling in CFS)

[Anthony Liguori]

On 01/03/2012 04:31 PM, Dor Laor wrote:
> > We can just set this for pc-1.1. I don't see any real harm in doing that.
>
> Great, it 'only' took about 3 years from the time it got developed originally by
> Uri...

Someone just needs to send a patch.

> > When using 'guests-pick', we initially present the most compatible
> > network model (rtl8139, for instance). We would provide a paravirtual
> > channel (guest-agent?) that could be used to enumerate which models were
> > available and let guest decide which model to use for the next reboot.
> > You could also enable immediate switch over using hot plug.
>
> If guest uses an agent, it probably has virtio-serial driver and it indicates it
> has other virtio ones, otherwise, the agent won't fly

Right, but I still you want the ability for the guest to indicate that it would 
like to use virtio drivers or not.

If you think about it, it makes no sense to choose which type of device gets 
used in the hypervisor.  In an ideal world, the guest would just figure out what 
it wants to see and get that.

The same is probably true about most device model properties.  rtc clock slew 
policy is another good example.  Instead of trying to figure out what the guest 
type is, we should just let the guest request device model settings like that.

> > > We need to keep on recommending the best profile for virtualization,
> > > for Fedora
> > > I think it either enterprise-storage and maybe throughput-performance.
> >
> > I think that's more of a distro. It might be worth referring to in our
> > documentation but I'm not sure it's something we can do much about.
>
> Someone said on the kvm community call today: "no one reads documentation", so
> it better be a script. As noted about we do have it in my favorite distribution,
> I hoped all distributions gets it.

Indeed, "referring to it in our documentation" was a polite way of saying, it's 
a distro problem :-)

The distro should let you choose a profile during installation or something like 
that.

Regards,

Anthony Liguori

> > Regards,
> >
> > Anthony Liguori
> >
> > > If we have a such a script, it can call the matching tuned profile
> > > instead of
> > > tweaking every /sys option.
> > >
> > > > Regards,
> > > >
> > > > Anthony Liguori
> > > >
> > > > > HTH,
> > > > > Dor