On Wed, 10 Jun 2009 03:56:31 pm Dor Laor wrote: > Rusty Russell wrote: > > The current theoretical hole is that the host suppresses notifications > > using the VIRTIO_AVAIL_F_NO_NOTIFY flag, but we can get a number of > > notifications in before it gets to that suppression. You can use a > > counter to improve this: you only notify when they're equal, and inc when > > you notify. That way you suppress further notifications even if the > > other side takes ages to wake up. In practice, this shouldn't be played > > with until we have full aio (or equiv in kernel) for other side: host > > xmit tends to be too fast at the moment and we get a notification per > > packet anyway. > > Xen ring has the exact optimization for ages. imho we should have it > too, regardless of aio. > It reduces #vmexits/spurious wakeups and it is very simple to implement. But look at number of wakeups received vs notifications sent: I just don't see any benefit there at the moment. As I said, improving the host code might change that significantly. And implementing it the other way is v. v. hard given the nature of interrupts (shared and coalesced). Thanks, Rusty. -- 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
