On Mon, Oct 04, 2010 at 09:01:14AM -0500, Anthony Liguori wrote: > On 10/04/2010 03:04 AM, Avi Kivity wrote: > > On 10/04/2010 03:18 AM, Anthony Liguori wrote: > >>On 10/03/2010 09:28 AM, Michael S. Tsirkin wrote: > >>> > >>>>This is using eventfd as well. > >>>Sorry, I meant irqfd. > >> > >>I've tried using irqfd in userspace. It hurts performance quite > >>a bit compared to doing an ioctl so I would suspect this too. > >> > >>A last_used_idx or similar mechanism should help performance > >>quite a bit on top of ioeventfd too. > >> > > > >Any idea why? While irqfd does quite a bit of extra locking, it > >shouldn't be that bad. > > Not really. It was somewhat counter intuitive. > > A worthwhile experiment might be to do some layering violations and > have vhost do an irq injection via an ioctl and see what the > performance delta is. I think you don't even need to try that hard. Just comment this line: // proxy->pci_dev.msix_mask_notifier = virtio_pci_mask_notifier; this is what switches to irqfd when msi vector is unmasked. > I suspect it could give vhost a nice boost. > > Regards, > > Anthony Liguori -- 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
