Re: [Bloat] Measuring CoDel

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

On Sat, 23 Jan 2021 01:34:19 +0100
Toke Høiland-Jørgensen via Bloat <bloat@lists.bufferbloat.net> wrote:

> Hal Murray <hmurray@megapathdsl.net> writes:
> 
> > Toke said:  
> >> Yeah, the overhead of CoDel itself (and even FQ-CoDel) is basically nil (as
> >> in, we have not been able to measure it), when otherwise doing forwarding
> >> using the regular Linux stack.   
> >
> > I may be able to help with that.
> >
> > Are you familiar with Dick Sites' KUtrace?
> >   Stanford Seminar - KUtrace 2020
> >   https://www.youtube.com/watch?v=2HE7tSZGna0  
> 
> Nope - but from a quick glance it looks similar to what you can do with
> 'perf'? :)

Yes, but the 'perf' tool (mostly) uses sampling.

I assume you want to catch latency outliers, right?

I would probably recommend that you play with bpftrace[1], for
processing all the events to catch the outliers.

 [1] https://github.com/iovisor/bpftrace

As an example look at this bpftrace script[2], that I used for
detecting latency issues, network hardIRQ-to-softirq latency.

 [2] https://github.com/xdp-project/xdp-project/blob/master/areas/latency/softirq_net_latency.bt
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer