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

[Gaëtan Rivet]

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.

For automated testing, what I did was open a pipe to testpmd to issue
commands from wherever, allowing to keep testpmd running in the
background and dispatch commands when needed from other terminals. No
need to issue signals at all then.

> 
> I do not see a big difference between "enter" and "ctrl+c".
> 
> I think it is more flexible to pipe commands instead of options.
> We could combine the proposed options --tx-first and -T into this command:
> ( echo 'start tx_first' ; while true ; do echo 'show port stats all' ; sleep 1 ; done ) | testpmd -i 
> 
> It is even possible to add more actions in the loop, so it is less
> limited than the -T options.
> 
> It is a matter of deciding whether we prefer to implement more restricted
> options or leverage the shell to freely program non-interactive testpmd.

-- 
Gaëtan Rivet
6WIND