Re: [Qemu-devel] [QEMU patch 2/2] kvm: allow configuration of tsc deadline timer advancement

[Marcelo Tosatti]

On Wed, Dec 10, 2014 at 06:29:43PM +0100, Paolo Bonzini wrote:
> 
> 
> On 10/12/2014 18:27, Marcelo Tosatti wrote:
> > On Wed, Dec 10, 2014 at 06:09:19PM +0100, Paolo Bonzini wrote:
> >>
> >>
> >> On 10/12/2014 18:04, Marcelo Tosatti wrote:
> >>>> Please add an object property to the x86 CPU object.  It can then be
> >>>> configured with "-global" on the command line.
> >>>
> >>> Don't want to allow individual values for different CPUs. 
> >>> It is a per-VM property.
> >>
> >> Why?  It can cause busy waiting, it would make sense to make it stricter
> >> for realtime CPUs and leave 0 for non-realtime CPUs.
> >>
> >> Paolo
> > 
> > HW timer behaviour should be consistent across CPUs, IMO.
> 
> It's not going to be anyway.  Cache line bounces, frequency scaling,
> presence of higher-priority RT tasks, etc. can cause different response
> for one CPU over the others.
> 
> Paolo

OK i'll change it to per-CPU.