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

[Bruce Richardson]

On Tue, Jun 20, 2017 at 12:19:01PM +0200, Gaëtan Rivet wrote:
> On Tue, Jun 20, 2017 at 11:58:54AM +0200, Thomas Monjalon wrote:
> > 20/06/2017 11:22, Bruce Richardson:
> > > On Mon, Jun 19, 2017 at 11:12:53PM +0200, Thomas Monjalon wrote:
> > > > 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 at 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
> > > > ?
> > > 
> > > The one big difference I see is normal vs abnormal termination. With the
> > > echo command you suggest, the only way to terminate testpmd is to kill
> > > it via signal. With the extra cmdline option, it will cleanly exit via
> > > enter as with non-interactive mode right now. Not a huge difference, but
> > > I think having the extra argument to enable tx-first is useful.
> 
> Side note, one can:
> 
> (trap 'echo quit' SIGUSR1; echo 'start'; while true; do sleep 1; done) |testpmd -i &
> 
> and issue a SIGUSR1 to the subshell to cleanly quit testpmd.
> Or:
> 
> (trap 'echo show port stats all' SIGUSR1; \
>  trap 'echo quit' SIGUSR2; \
>  echo 'start'; \
>  while true; do :; done) |\
> testpmd -i &
> 
> It's a little contrived, but it does the job and is easy enough to put
> in scripts.
> 
Or we can just put in a --tx-first flag and save the user the pain of
doing multi-line bash commands. Usability is a constant complaint about
DPDK that we hear e.g. at userspace every year, so we need to stop
assuming everyone looking to play with DPDK is a shell power-user.

/Bruce