On 09/07/12 08:20, Raghavendra K T wrote: > Currently Pause Looop Exit (PLE) handler is doing directed yield to a > random VCPU on PL exit. Though we already have filtering while choosing > the candidate to yield_to, we can do better. > > Problem is, for large vcpu guests, we have more probability of yielding > to a bad vcpu. We are not able to prevent directed yield to same guy who > has done PL exit recently, who perhaps spins again and wastes CPU. > > Fix that by keeping track of who has done PL exit. So The Algorithm in series > give chance to a VCPU which has: We could do the same for s390. The appropriate exit would be diag44 (yield to hypervisor). Almost all s390 kernels use diag9c (directed yield to a given guest cpu) for spinlocks, though. So there is no win here, but there are other cases were diag44 is used, e.g. cpu_relax. I have to double check with others, if these cases are critical, but for now, it seems that your dummy implementation for s390 is just fine. After all it is a no-op until we implement something. Thanks Christian -- 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
