On Tue, Nov 13, 2012 at 05:35:55PM +0100, Peter Lieven wrote: > > Am 13.11.2012 um 17:33 schrieb Michael S. Tsirkin: > > > On Tue, Nov 13, 2012 at 06:22:56PM +0200, Michael S. Tsirkin wrote: > >> On Tue, Nov 13, 2012 at 12:49:03PM +0100, Peter Lieven wrote: > >>> > >>> On 09.11.2012 19:03, Peter Lieven wrote: > >>>> Remark: > >>>> If i disable interrupts on CPU1-3 for virtio the performance is ok again. > >>>> > >>>> Now we need someone with deeper knowledge of the in-kernel irqchip and > >>>> the > >>>> virtio/vhost driver development to say if this is a regression in > >>>> qemu-kvm > >>>> or a problem with the old virtio drivers if they receive the interrupt on > >>>> different CPUs. > >>> anyone? > >> > >> Looks like the problem is not in the guest: I tried ubuntu guest > >> on a rhel host, I got 8GB/s with vhost and 4GB/s without > >> on a host to guest banchmark. > >> > > > > Tried with upstream qemu on rhel kernel and that's even a bit faster. > > So it's ubuntu kernel. vanilla 2.6.32 didn't have vhost at all > > so maybe their vhost backport is broken insome way. > > That might be. I think Dietmar was reporting that he had problems > with Debian. They likely use the same back port. > > Is it correct that with kernel_irqchip the IRQs are > delivered to all vCPUs? Without kernel_irqchip (in qemu-kvm 1.0.1 > for instance) they where delivered only to vCPU 0. This scenario > was working. > > Peter
You need to look at how MSI tables are programmed to check if it's OK - guest can program MSI to do it like that. pciutils does not do this unfortunately so you'll have to write a bit of C code if you want to do this. -- MST