On Fri, Apr 17, 2015 at 12:38:07PM +0200, Paolo Bonzini wrote:
>
>
> On 17/04/2015 12:36, Peter Zijlstra wrote:
> > Now you make everybody pay for your crap, x86-64 paravirt or not. Keep
> > the cost by those who need it.
> >
> > Please take it out, ASAP.
>
> I'll just implement the static key.
Can you first show that:
preempt_out:
int cpu = smp_processor_id();
if (vcpu->cpu != cpu)
vcpu->cpu = cpu;
preempt_in:
int cpu = smp_processor_id();
if (unlikely(vcpu->cpu != cpu))
do_vcpu_migration_callback(cpu);
Is actually a measurable performance hit and we actually _need_ the
migration callback?
Also, it looks like you already do exactly this for other things, look
at:
kvm_sched_in()
kvm_arch_vcpu_load()
if (unlikely(vcpu->cpu != cpu) ... )
So no, I don't believe for one second you need this.
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