id summary reporter owner description type status component version resolution keywords cc guest host 11154 Bad VM to Host Network Performance with Intel NIC or virtio Gevatter Gaul "I'm running VirtualBox 4.2 on a Ubuntu 12.04 LTS 64bit. The machine is a Xeon E1230 Quadcore with 32G ECC RAM. The VM, running Ubuntu 12.04 LTS 64bit, is connected via a Host Adapter. When running a ping from the Host to the VM, everything seems fine and I get an average latency of around 0.2ms. But in the other direction, depending on the configured VM NIC, I get very high ping results. Strangely enough, the problem only exists, when configuring more than one virtual CPU. Here are my measurements: Average Ping: VCPUs PCnet-PCI II PCnet-FAST III Intel PRO/1000 MT Desktop Intel PRO/1000 T Server Intel PRO/1000 MT Server Paravirtualized Network 1 0.168 0.183 0.209 0.191 0.206 0.399 2 0.193 0.182 15.987 12.157 10.349 5.327 3 0.179 0.167 12.032 14.052 9.657 5.337 4 0.174 0.176 12.929 13.680 13.627 5.482 mdev: VCPUs PCnet-PCI II PCnet-FAST III Intel PRO/1000 MT Desktop Intel PRO/1000 T Server Intel PRO/1000 MT Server Paravirtualized Network 1 0.043 0.046 0.040 0.061 0.039 0.055 2 0.085 0.085 16.036 16.390 14.946 4.638 3 0.045 0.046 14.575 16.903 13.330 5.252 4 0.045 0.044 16.286 16.033 16.148 4.881 We see, as soon as I configure more than one VCPU, latency goes through the roof. vbox guest log and showvminfo output are attached." defect closed network/hostif VirtualBox 4.2.4 duplicate nic intel ping latency bug performance Linux Linux