On Mon, 2021-10-25 at 16:26 +0200, Paolo Bonzini wrote: > On 09/10/21 04:12, Sean Christopherson wrote: > > Calculate the halt-polling "stop" time using "cur" instead of redoing > > ktime_get(). In the happy case where hardware correctly predicts > > do_halt_poll, "cur" is only a few cycles old. And if the branch is > > mispredicted, arguably that extra latency should count toward the > > halt-polling time. > > > > In all likelihood, the numbers involved are in the noise and either > > approach is perfectly ok. > > Using "start" makes the change even more obvious, so: > > Calculate the halt-polling "stop" time using "start" instead of redoing > ktime_get(). In practice, the numbers involved are in the noise (e.g., > in the happy case where hardware correctly predicts do_halt_poll and > there are no interrupts, "start" is probably only a few cycles old) > and either approach is perfectly ok. But it's more precise to count > any extra latency toward the halt-polling time. > > Paolo > Agreed. Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
