On Tue, Sep 15, 2009 at 05:15:09PM +0200, Luca Bigliardi wrote: > Hi, > I'm running some tests between two linux instances bridged together. > > If I try to ping 10 times I obtain the following results: > > -net nic,model=virtio -net tap : > rtt min/avg/max/mdev = 0.756/0.967/2.115/0.389 ms > > -net nic,model=rtl8139 -net tap : > rtt min/avg/max/mdev = 0.301/0.449/1.173/0.248 ms > > So it seems with virtio the latency is higher. Is it normal? Yes, the main reason is the TX timer it uses for interrupt/vm exit mitigation. > The results I'm reporting were obtained with > - host > qemu-kvm 0.11-rc2 > kvm-kmod-2.6.30.1 > kernel: 2.6.30.5 (HIGH_RES_TIMERS=y as suggested in > http://www.linux-kvm.org/page/Virtio ) > - guest > kernel: 2.6.31 > > but I also tested older versions always obtaining latency values at least two > times higher than rtl8139/e1000 . > > Thank you, > Luca > > -- > 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 -- 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
