Re: [Qemu-devel] Re: Network Performance between Win Host and Linux

["Kenneth Duda" <kduda@arastra.com>]

Leo, thank you for exercising this stuff.

> 1. before your patches, the upstream transfers (guest->host) consumed
> almost no CPU at all, but of course were much slower.  Now, about half
> the CPU gets used under heavy upstream load.

I am surprised that only half the CPU gets consumed --- that suggests
there's another factor of two improvement waiting to be made.  If you
see anything like this with Linux-on-Linux, please let me know and
I'll try to track it down.

Separately, I'm curious about the path for getting these changes into
the qemu mainline.  If that's something you're in tune with and are in
the mood to summarize for me, I'd appreciate that.  We love qemu but
there are some rough edges and I think we have something like 16
patches we're maintaining internally, many of which might be helpful
for others.

     -Ken

On 4/12/06, Leonardo E. Reiter <lreiter@win4lin.com> wrote:
> Hi Ken,
>
> (all) the patches seem to work very well and be very stable with Windows
> 2000 guests here.  I measured some SMB over TCP/IP transfers, and got
> about a 1.5x downstream improvement and a 2x upstream improvement.  You
> will likely get more boost from less convoluted protocols like FTP or
> something, but I didn't get around to testing that.  Plus it's not clear
> how much Windows itself is impeding the bandwidth.  I am using
> -kernel-kqemu.
>
> 2 additional things I noticed:
>
> 1. before your patches, the upstream transfers (guest->host) consumed
> almost no CPU at all, but of course were much slower.  Now, about half
> the CPU gets used under heavy upstream load.  The downstream, with
> Windows guests at least, consumes 100% CPU the same as before.  I
> suspect you addressed this specifically with your select hack to avoid
> the delay if there is pending slirp activity
>
> 2. overall latency "feels" improved as well, at least for basic stuff
> like web browsing, etc.  This is purely subjective.
>
> Nice work!  I'll be testing with a Linux VM soon and try to pin down
> some better benchmarks, free of Windows clutter.
>
> - Leo Reiter