Re: Improving user networking performance

[Paul Menzel]

Dear Anders,


Am 07.04.22 um 22:27 schrieb Anders Pitman:

> Thanks for the response. I've collected more precise data for you.

Thank you.

> > Please share the command line, how you start the GNU/Linux VM, and
> > what GNU/Linux distribution you use.
>
> I'll share the specific command lines with the results data below.
> For the distro, I'm using buildroot-2022.02. I started with the
> configs/qemu_x86_64_defconfig file. Kernel 5.15.18. It's also set up
> to bundle the cpio initramfs inside the kernel image, includes
> iperf3, and e1000 drivers.
>
> > Please be specific. What kind of laptop (CPU, …)?
>
> It's an old Lenovo x220 laptop. Intel Core i5-2520M. 2 hyperthreaded
> cores. 2.5GHz. 8GB memory.

Nice. If you are interested in FLOSS firmware, see coreboot [1]. ;-)

> > How do you measure the transfer speed?
>
> I'm using iperf3. It's running on the Windows 10 host using MSYS2, like so:
>
> iperf3 -s
>
> And from the guest like so:
>
> iperf3 -c 10.0.2.2
>
> Results:
>
> As a baseline, I ran iperf3 over localhost on the host machine. Both
> client and server were running
> from MSYS2 with iperf3 installed using pacman -S iperf3. Results:
>
> 1.37Gbits/sec
>
> For the remaining tests, I ran iperf from the guest to host like so:
>
> iperf3 -c 10.0.2.2
>
> qemu-system-x86_64.txt -kernel bzImage -append "console=ttyS0" -nic user,e1000
>
> 45.1Mbits/sec
>
> qemu-system-x86_64.txt -kernel bzImage -append "console=ttyS0" -nic user,virtio
>
> 33.9Mbits/sec
>
> qemu-system-x86_64.txt -kernel bzImage -append "console=ttyS0" -nic user,e1000 
> -accel whpx
>
> 63.5Mbits/sec
>
> qemu-system-x86_64.txt -kernel bzImage -append "console=ttyS0" -nic user,virtio 
> -accel whpx
>
> 83.4Mbits/sec
>
> qemu-system-x86_64.txt -kernel bzImage -append "console=ttyS0" -nic user,virtio 
> -accel whpx -m 4096 -smp 4
>
> 63.9Mbits/sec
>
> Notes:
>
> * virtio+whpx is the fastest, but virtio without whpx is slower than e1000.
> * None of the tests are saturating the host CPU. In fact CPU usage according to 
> Task Manager stays below ~20%.
> * I get fairly different results from run to run for the same test. As much as 
> +/- 10Mbits/sec observed so far.
> * Apparently -cpu host doesn't work on Windows hosts?

Thank you for the detailed data. Unfortunately, I have no idea about 
running QEMU under Microsoft Windows, but could imagine, that it’s not 
very optimized. Also, I wonder if using VirtIO is possible with 
Microsoft Windows host. Does it implement that interface?

To rule out it’s Microsoft Windows related, you could see if it works 
better with a GNU/Linux host, for example a live distribution. And you 
could also try to run QEMU in WSL (Windows Subsystem for Linux) and see 
if that works better.


Kind regards,

Paul


[1]: https://doc.coreboot.org/mainboard/lenovo/Sandy_Bridge_series.html