On Thu, Aug 10, 2017 at 02:46:00PM +1000, Benjamin Herrenschmidt wrote: > On Thu, 2017-08-10 at 14:28 +1000, David Gibson wrote: > > > > Also, will POWER9 always have doorbells? In which case you could > > reduce it to 3 options. > > The problem with doorbells on POWER9 guests is that they may have > to trap and be emulated by the hypervisor, since the guest threads > on P9 don't have to match the HW threads of the core. > > Thus it's quite possible that using XIVE for IPIs is actually faster > than doorbells in that case.
Ok, well unless there's a compelling reason to use doorbells you can instead make it 3 cases with POWER9 never using doorbells. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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