Re: [Make-wifi-fast] less latency, more filling... for wifi

[Jesper Dangaard Brouer <brouer@redhat.com>]

Hi Bob,

Just wanted to let you know, that after you posted this, I've started
to use your iperf2 tool again.  To verify some of my kernel code.

I particularly liked that I can send with a specific PPS rate, like:

 iperf2-git -c 172.16.0.2 -e -u -b 20000pps -i 1


On Mon, 9 Oct 2017 14:04:35 -0700 Bob McMahon <bob.mcmahon@broadcom.com> wrote:

> Not sure if this is helpful but we've added end/end latency measurements
> for UDP traffic in iperf 2.0.10 <https://sourceforge.net/projects/iperf2/>.

I tried it out, but the clock between my two machines are not accurate
enough (as you hint below).

>   It does require the clocks to be synched.  I use a spectracom tsync pcie
> card with either an oven controlled oscillator or a GPS disciplined one,
> then use precision time protocol to distribute the clock over ip
> multicast.  

> For Linux, the traffic threads are set to realtime scheduling
> to minimize latency adds per thread scheduling..

If I use the --realtime option, I did run into issues where the server
thread would busypoll 100% after e.g. a client stopped a test prematurely.
And I had to kill it with -9.

Thanks for you work!
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer