On Fri, Sep 9, 2016 at 9:38 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 09/09/2016 00:13, David Matlack wrote: >> Hi Paolo, >> >> On Tue, Sep 6, 2016 at 3:29 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >>> Bad things happen if a guest using the TSC deadline timer is migrated. >>> The guest doesn't re-calibrate the TSC after migration, and the >>> TSC frequency can and will change unless your processor supports TSC >>> scaling (on Intel this is only Skylake) or your data center is perfectly >>> homogeneous. >> >> Sorry, I forgot to follow up on our discussion in v1. One thing we >> discussed there was using the APIC Timer to workaround a changing TSC >> rate. You pointed out KVM's TSC deadline timer got a nice performance >> boost recently, which makes it preferable. Does it makes sense to >> apply the same optimization (using the VMX preemption timer) to the >> APIC Timer, instead of creating a new dependency on kvmclock? > > Hi, yes it does. If we go that way kvmclock.c should be patched to > blacklist the TSC deadline timer. However, I won't have time to work on > it anytime soon, so _if I get reviews_ I'll take this patch first. Got it, thanks for the context. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
