On 07/09/2012 10:55 AM, Christian Borntraeger wrote: > 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.
Perhaps x86 should copy this. > 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. Does the data structure make sense for you? If so we can move it to common code (and manage it in kvm_vcpu_on_spin()). We can guard it with CONFIG_KVM_HAVE_CPU_RELAX_INTERCEPT or something, so other archs don't have to pay anything. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
