[libvirt] [PATCH] Fix virsh sched-credit for xend

[Daniel P. Berrange]

On Mon, Jan 26, 2009 at 10:55:37AM +0000, Richard W.M. Jones wrote:
> On Fri, Jan 23, 2009 at 10:34:14AM +0000, Daniel P. Berrange wrote:
> > On Thu, Jan 22, 2009 at 05:49:00PM -0800, john.levon at sun.com wrote:
> > > # HG changeset patch
> > > # User john.levon at sun.com
> > > # Date 1232675291 28800
> > > # Node ID 415bfd87e0ecd7751ed6df372e82da0e3991d617
> > > # Parent  68e14fe50dfa88a4694bc4c7a68d2f73f41c6171
> > > Fix virsh sched-credit for xend
> > > 
> > > Need to pass domain in the xend op for shut-down domains.
> > > (This also requires xend fixes, but this patch doesn't make things
> > > worse.)
> > 
> > Does XenD actaully persist the schedinfo changes for inactive domains ?
> > Historically we've only considered the sched tunables API to be
> > relevant to active guests, and none of the drivers make any attempt
> > to persist the settings for inactive domains.
> 
> I'm not sure if we make any explicit guarantees about this though, so
> perhaps we should leave the decision to the drivers themselves?  Or
> document how it should work in the API?

It isn't that simple. Tunables are not represented as part of the XML,
and if Xen is now persisting them in its config file, then any statement
we make about virDomainSetSchedularParams persisting the settings would
be unreliable. The very next call to virDomainDefineXML/CreateXML will
blow away the tunable settings that were not part of the XML.

So if we want to be able to set tunables on inactive domains, the 
virDomainSetSchedularParams() is not the right place todo it - we
can only guarentee that is is reliably usable on live domains. 

Daniel
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