[dpdk-dev] [RFC] DPDK Trace support

[Bruce Richardson]

On Mon, Jan 13, 2020 at 08:16:07PM +0530, Jerin Jacob wrote:
> On Mon, Jan 13, 2020 at 6:36 PM Bruce Richardson
> <bruce.richardson at intel.com> wrote:
> >
> >
> > > So, Probably it good to have native CTF emitter in DPDK and reuse all
> > > open-source trace viewer(babeltrace and  TraceCompass) and format(CTF) infrastructure.
> > > I think, it would be best of both world.
> > >
> > > Any thoughts on this subject? Based on the community feedback, I can work on the patch for v20.05.
> >
> > Forgive my ignorance of LTTng, but is there the concept of
> > enabling/disabling the trace points? If so, the overhead you refer to, that
> > is presumably with the trace enabled?
> 
> Yes this is when trace is enabled. If the trace is disabled then it
> will be the only a handful of cycles.
> 
Two follow-on questions:
1. Is the trace enable/disable dynamic at runtime?
2. Have you investigated how low the "handful of cycles" actually is?

While I think it is important to get the cost of tracing right down to make
it useful, the cost of tracing when it is not being used is even more
critical IMHO.

/Bruce