And I just pushed a branch that calculates a timer interval based on the
throttle rate and the buffer size, with a cap on the timer frequency that
can be changed via the command-line.  It _seems_ to work well, and give
really smooth pacing.  Incredibly smooth pacing, actually (at least at 1ms
time bucket intervals).

The branch is here:  https://github.com/woody77/iperf/tree/pacing_timer

-Aaron

On Tue, Sep 20, 2016 at 4:32 PM, Aaron Wood <woody77@gmail.com> wrote:

> On Tue, Sep 20, 2016 at 3:03 PM, Dave Täht <dave@taht.net> wrote:
>
>> Groovy. I note that I am really fond of the linux "fdtimer" notion for
>> tickers, we use that throughout the high speed stats gathering code in
>> flent.
>>
>> I'd really like a voip or ping tool that used those, and I've always
>> worried about iperf's internal notion of a sampling interval.
>>
>> On 9/20/16 3:00 PM, Aaron Wood wrote:
>> > I modified iperf3 to use a 1ms timer, and was able to get things much
>> > smoother.  I doubt it's as smooth as iperf3 gets on Linux when fq pacing
>> > is used, but it's a big improvement vs. the nice small buffers in
>> switches.
>>
>
> Thanks!
>
> For rates of <1000 packets per second, the 1ms timer I put in will give
> something like that (it fires every ms, but that's just a check for sending
> or not).  If you want to use it to model a 120pps flow of 64-byte packets:
>
> iperf3 -c <host> -u -l 64 -b 61440
>
> And then it will pace those out at roughly every 80ms (just verified this
> on my box)
>
> -Aaron
>