On Mon, Oct 12, 2009 at 10:16:56AM +0200, Jan Kiszka wrote: > >>> Apic is lockless. For ioapic/pic I used spinlocks initially, but Avi > >>> prefers mutexes. Theoretically it is possible to make them lockless, > >>> but code will be complex and eventually more slow, since more then two > >>> atomic operation will be used on irq injection path. > >> Well, lockless is another thing. > >> > >> But also converting to spinlocks would indeed add some overhead: > >> irqsave/restore. But I wonder if this isn't worth it, at least when > >> looking at the (supposed to be fast) device passthrough scenario which > >> would be simpler and faster. > >> > > Avi's point in favor of mutex is: they are as fast as spinlocks when > > congested and allows preemption when held. > > ...but require scheduler activity in case of dev-passthrough, which is > surely playing in a different league. > I'd rather remove dev-passthrough completely than continue adding hack upon hack upon hack to make is some times kinda sorta work :) -- Gleb. -- 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
