Paolo Bonzini wrote on 2015-04-24: > > > On 24/04/2015 03:16, Zhang, Yang Z wrote: >>> This is interesting since previous measurements on KVM have had the >>> exact opposite results. I think we need to understand this a lot >>> more. >> >> What I can tell is that vmexit is heavy. So it is reasonable to see >> the improvement under some cases, especially kernel is using eager >> FPU now which means each schedule may trigger a vmexit. > > On the other hand vmexit is lighter and lighter on newer processors; a > Sandy Bridge has less than half the vmexit cost of a Core 2 (IIRC 1000 > vs. 2500 clock cycles approximately). > 1000 cycles? I remember it takes about 4000 cycle even in HSW server. > Also, measurement were done on Westmere but Sandy Bridge is the first > processor to have XSAVEOPT and thus use eager FPU. > > Paolo Best regards, Yang -- 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
