Virtio io path vhost io path and vhost-user vhost-user ********* network device

With the release of qemu2.1, you can see that QEMU supports Vhost-user. From the introduction can be seen, this is the original vhost-backend from kernel moved to the userspace, this and the original virtio structure what is the difference. And this feature has brought about improvements. Virtio

In the virtual machine, you can simulate the E1000 network card through QEMU, such classic network card is a general variety of customer operating system will provide Inbox drive, so from the compatibility point of view, the use of similar e1000 analog network card is a very good choice.

However, the E1000 network card also contains a complex IO port, register, cache configuration, the virtual machine each receiver will cause more IO and mmio operations, making the virtual machine frequently trapped, resulting in poor network performance.

To address performance issues, IBM introduced the Virtio in 2005, in which the semi virtualized front-end driver in the virtual machine and the back-end service on the host simply used Virtqueue shared queues to exchange data, dramatically reducing the complexity of IO operations in e1000 simulations, So as to improve the performance of virtual network to a large extent.

In contrast, from the simple iperf test below, we can see the performance gap between the two:

With Virtio

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------------------------------------------------------------Client connecting to Virtio, TC P Port 5001 TCP window size:16.0 KByte (default)---------------------------------------------- -- -- -- -- -- -- --