Re: [dpdk-dev] [PATCH v3] app/testpmd: add parameter to start forwarding TX first

["De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas@monjalon.net]
> Sent: Monday, June 19, 2017 10:13 PM
> To: De Lara Guarch, Pablo
> Cc: dev@dpdk.org; Wu, Jingjing
> Subject: Re: [dpdk-dev] [PATCH v3] app/testpmd: add parameter to start
> forwarding TX first
> 
> 15/06/2017 14:05, De Lara Guarch, Pablo:
> > > Add parameter to start forwarding sending first
> > > a burst of packets, which is useful when testing
> > > a loopback connection.
> > >
> > > This was already implemented as an internal command,
> > > but adding it as a parameter is interesting, as it
> > > allows the user to test a loopback connection without
> > > entering in the internal command line.
> > >
> > > Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
> > > ---
> > > --- a/doc/guides/testpmd_app_ug/run_app.rst
> > > +++ b/doc/guides/testpmd_app_ug/run_app.rst
> > > @@ -188,6 +188,14 @@ The commandline options are:
> > >
> > >      Start forwarding on initialization.
> > >
> > > +*   ``--tx-first``
> > > +
> > > +    Start forwarding, after sending a burst of packets first.
> > > +
> > > +.. Note::
> > > +
> > > +   This flag should be only used in non-interactive mode.
> 
> I don't really understand the benefit of this option.
> Why is it better than
> 	echo start tx_first | testpmd -i
> ?

This is a good way to test a loopback connection without having to get into interactive mode.
With the other patch that I sent, to show port statistics periodically
(http://dpdk.org/dev/patchwork/patch/25344/), the app can show how traffic is forwarded
having a simple loopback connection, without anything else required by the user.

Thanks,
Pablo