On Mon, Nov 08, 2010 at 12:21:44PM +0100, Jan Kiszka wrote: > Nine patches (yeah, it's getting more and more) to improve "classic" > device assigment /wrt IRQs. Highlight is the last one that resolves the > host IRQ sharing issue for all PCI 2.3 devices. Quite essential when > passing non-MSI-ready devices like many USB host controllers. > > As there were concerns regarding the overhead of IRQ masking via the PCI > config space, I did some micro-benchmarks. Well, the concerns are valid: > > disable_irq_nosync: ~600 cycles > pci_2_3_irq_check_and_mask: ~6000 cycles (EHCI) > ~22000 cycles (AR9287, with peaks >100000) > > Specifically the varying impact of the device like in the Atheros case > is worrying (this device is actually known to cause horrible latencies > to the host, but who knows what other devices do). So I decided to go > with PCI-2.3 masking as default off in the to-be-sent qemu-kvm patch. > Maybe something to consider vor VFIO as well. Looks fine to me. Michael, Alex? Also needs a rebase. -- 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
