Michael S. Tsirkin wrote: > On Mon, Jul 13, 2009 at 04:32:34PM +0300, Gleb Natapov wrote: > >> Yeah I understand that other RCU read section may introduce delays too. >> The question is how big the delay may be. >> > > I recall seeing the number "at least 3 jiffies" somewhere, but that > might have changed since. > I think it is dependent on how you configure your kernel...but that sounds ballpark for one of the worst-case types IIRC. > >> I don't think multiple >> milliseconds delay in device de-assignment is a big issue though. >> > > Right. My point was that since the sync is done under kvm lock, the > guest can easily get blocked trying to get kvm lock meanwhile. > Yeah, that is really the biggest issue here, I agree. The delay in the actual deassignment path is NBD. Kind Regards, -Greg
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