Re: [dpdk-dev] L3fwd mode in testpmd

[Jerin Jacob <jerinjacobk@gmail.com>]

On Thu, Apr 1, 2021 at 2:05 AM Kathleen Capella
<Kathleen.Capella@arm.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
> > Sent: Thursday, March 11, 2021 11:00 AM
> > To: thomas@monjalon.net
> > Cc: Jerin Jacob <jerinjacobk@gmail.com>; dev@dpdk.org; Kathleen Capella
> > <Kathleen.Capella@arm.com>; Dharmik Thakkar
> > <Dharmik.Thakkar@arm.com>; Ruifeng Wang <Ruifeng.Wang@arm.com>;
> > david.marchand@redhat.com; Bruce Richardson
> > <bruce.richardson@intel.com>; jerinj@marvell.com;
> > hemant.agrawal@nxp.com; Ferruh Yigit <ferruh.yigit@intel.com>; Ananyev,
> > Konstantin <konstantin.ananyev@intel.com>; Stephen Hemminger
> > <sthemmin@microsoft.com>; nd <nd@arm.com>; nd <nd@arm.com>
> > Subject: RE: [dpdk-dev] L3fwd mode in testpmd
> >
> > <snip>
> >
> > > >
> > > > >
> > > > > On Thu, Mar 11, 2021 at 12:01 AM Honnappa Nagarahalli
> > > > > <Honnappa.Nagarahalli@arm.com> wrote:
> > > > > >
> > > > > > Hello,
> > > > > >         Performance of L3fwd example application is one of the
> > > > > > key
> > > > > benchmarks in DPDK. However, the application does not have many
> > > > > debugging statistics to understand the performance issues. We have
> > > > > added L3fwd as another mode/stream to testpmd which provides
> > > enough
> > > > > statistics at various levels. This has allowed us to debug the
> > > > > performance issues effectively.
> > > > > >
> > > > > > There is more work to be done to get it to upstreamable state. I
> > > > > > am
> > > > > wondering if such a patch is helpful for others and if the
> > > > > community would be interested in taking a look. Please let me know
> > what you think.
> > > > >
> > > > > We are using app/proc-info/ to attach and analyze the performance.
> > > > > That helps to analyze the unmodified application. I think, if
> > > > > something is missing in proc-info app, in my opinion it is better
> > > > > to enhance proc-info so that it can help other third-party applications.
> > > > >
> > > > > Just my 2c.
> > > > Thanks Jerin. We will explore that.
> > >
> > > I agree it is dangerous to rely too much on testpmd for everything.
> > > Please tell us what in testpmd could be useful out of it.
> > >
> > Things that are very helpful in testpmd are: 1) HW statistics from the NIC 2)
> > Forwarding stats 3) Burst stats (indication of headroom availability) 4) Easy to
> > set parameters like RX and TX queue depths (among others) without having
> > to recompile.
>
> [Kathleen Capella]
> Thank you for the suggestion of app/proc-info. I've tried it out with
> l3fwd and see that it does have the HW stats from the NIC and the forwarding stats.
> However, it does not have the burst stats testpmd offers, nor the

One option to see such  level of debugging would be to have
- Create a memzone in the primary process
- Application under test can update the stats in memzone based on the code flow
- proc-info can read the counters updated by application under test
using the memzone object got through rte_memzone_lookup()

Another approach will be using rte_trace()[1] for debugging/tracing by
adding tracepoints in l3fwd for such events.
It has a timestamp and the trace format is opensource trace
format(CTF(Common trace format)), so that we can use
post posting tools to analyze.
[1]
https://doc.dpdk.org/guides/prog_guide/trace_lib.html


> ability to easily change parameters without having to recompile,
> which helps reduce debugging time significantly.