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



* Dave Allan <dallan redhat com> [2011-07-08 17:23:31]:

> On Mon, Jul 04, 2011 at 10:00:20PM +0530, Vaidyanathan Srinivasan wrote:
> > * Dave Allan <dallan redhat com> [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.

Let me get the next iteration of the patch out with working code.
This will allow us to review the implementation in more details.

Thanks,
Vaidy




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