Messages in this thread | | | Date | Fri, 17 Apr 2015 12:55:06 +0200 | From | Peter Zijlstra <> | Subject | Re: [GIT PULL] First batch of KVM changes for 4.1 |
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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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