[Qemu-devel] Fastest TCP/IP Stack

[Qemu-devel] Fastest TCP/IP Stack

[Joseph Miller]

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


-Joseph

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

[WaxDragon]

I've not done any benchmarks, but I do pay attention to resource
usage. (Host OS linux)  -net user has pretty good thoughput, but does
burn some cpu.  I think in that regard, -net tap has less overhead.
During my use of qemu, I've noticed that the quality of the nic driver
and the nic emulation itself comes into play.  I would try the
differnet models and see.  -net nic,model=pcnet always seemed like it
performed well. YOMV.

WD

On 9/14/06, Joseph Miller <it@tidetamerboatlifts.com> 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
>
>
> -Joseph
>
>
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>


-- 
22:38 <@WaxDragon> false ^ true
22:39 < false> :(
22:39 < false> dont you think you can XOR me and get away with it! I
always return!

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

[Ed Swierk]

On 9/14/06, Joseph Miller <it@tidetamerboatlifts.com> 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