Re: [Qemu-devel] Fastest TCP/IP Stack

[Ed Swierk]

On 9/14/06, Joseph Miller <address@hidden> wrote:
> I'm running a terminal server under qemu with kqemu compiled into my kernel
> under the -kernel-kqemu for fastest performance.  What is the most efficient
> method of -net ?  I was using -net user with OpenVPN to connect to my
> internal LAN, but I have switched to -net tap to see if that is faster.  Does
> anyone have any knowledge of which would take the least overhead?  I noticed
> on my top stats that my % sys was particularly high when using networking
> under -net user.  Thanks

-net tap is considerably more efficient than -net user in most cases.
-net user is a TCP/UDP proxy, so (a) your TCP connections are no
longer end-to-end, and (b) performance is at the mercy of qemu's
internal TCP/IP stack. With -net tap and a bridge, IP packets are
passed along unmolested, and all the magic occurs within the host
kernel.

(Of course where performance is not a pressing issue, -net user is
still awfully convenient.)

--Ed