On 08/05/2012 10:30 PM, Eric Northup wrote: > On Sun, Aug 5, 2012 at 5:58 AM, Gleb Natapov <[email protected]> wrote: >> APIC code has a lot of checks for apic presence and apic HW/SW enable >> state. Most common configuration is when each vcpu has in kernel apic >> and it is fully enabled. This path series uses jump labels to turn checks >> to nops in the common case. > > What is the target workload and how does the performance compare? As > a naive question, how different is it than just using gcc branch > hints?
We saw about 1.3% spent in kvm_apic_present() in some OLTP benchmark. I imagine most of it would be gone by just inlining. An exception would be the call from kvm_irq_delivery_to_apic() which happens from a different cpu, possibly causing a cache miss if something in the same cache line as vcpu->arch.apic is changed frequently. Come to think of it, if we implemented the irq routing cache (which eliminates the loop in kvm_irq_delivery_to_apic()) we might improve things quite a lot as well. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
