Re: [libvirt] [RFC] exporting KVM host power saving capabilities through libvirt

On Mon, Jul 04, 2011 at 10:00:20PM +0530, Vaidyanathan Srinivasan wrote: > * Dave Allan <dallan(a)redhat.com&gt; [2011-07-01 17:19:06]: > > > On Fri, Jul 01, 2011 at 04:56:29PM -0400, Dave Allan wrote: > > > On Tue, Jun 28, 2011 at 08:55:31PM +0530, Vaidyanathan Srinivasan wrote: > > > > Hi, > > > > > > > > Linux host systems running KVM support various power management > > > > capabilities. Most of the features like DVFS and sleep states can be > > > > independently exploited by the host system itself based on system > > > > utilisation subject to policies set by the administrator. > > > > > > > > However, system-wide low power states like S3 and S4 would require > > > > external communication and interaction with the systems management > > > > stack in order to be used. The first steps in this direction would be > > > > to allow systems management stack to discover host power saving > > > > capabilities like S3 and S4 along with various other host CPU > > > > capabilities. > > > > > > > > Libvirt seems to be the main glue layer between the platform and the > > > > systems-management stack. Adding host power savings capabilities as > > > > part of libvirt host discovery mechanism seems to be one possible > > > > approach without addition of any new APIs or agents. > > > > > > Can you provide the use cases you're looking to address with this > > > work? > > > > BTW, I'm intrigued by what you might be doing here, but I don't feel > > like I have enough information at this point to know quite what to > > think of it. > > Hi Dave, > > Thanks for taking a look. There are several advantages for using S3 > or S4 state for the host system instead power 'off' and 'on' for > starting new guest instances. The main advantage of discovering the > capability through the systems management stack is to get the > capability reported after checking against all policies and software > compatibilities. The overall idea is to allow high level systems > management software that work through libvirt to discover and exploit > these capabilities wherever possible. > > Discovery of available power savings features is only the first step > and I am looking for ideas to export these capabilities through > libvirt. I would expect the management stack that collects host > capabilities would be keep these feature list and could use them to > make various optimization decisions. That certainly sounds useful to me.