Re: [PATCH 2/2] blkback: Add default policy values for I/O QoS code

[William Pitcock <nenolod@dereferenced.org>]

On Tue, 2009-03-31 at 00:22 -0700, Jeremy Fitzhardinge wrote:
> William Pitcock wrote:
> > This patch adds default values which define a default QoS policy for
> > guest I/O. A sysctl interface will be added once /proc/sys/xen is available
> > again... unless I come up with a better idea in the meantime.
> >   
> 
> What would that interface look like?  Would the parameters be per 
> domain, or per device?  Would sysfs be suitable?

I was thinking about sysfs as an option, but xenstore also seems
desirable, since that way we can integrate QoS policy directly into the
vm config in an easy way without having to modify the userland tools in
any sort of major way.

Ian mentioned that netback uses xenstore for getting information, so I
think we could do the same here to get the QoS policy. It seems like a
sensible way.

Also, hopefully the dom0 base stuff will make it for 2.6.30. Can't wait
to have pvops-dom0 in production... keeping my fingers crossed on that
one. Although I could just backport this work to 2.6.18-xen.hg if it
comes down to being necessary to do so.

William