[dpdk-dev] [PATCH 2/6] testpmd: configurable tx_first burst number

[Wang, Zhihong]

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com]
> Sent: Wednesday, May 25, 2016 5:35 PM
> To: Wang, Zhihong <zhihong.wang at intel.com>
> Cc: dev at dpdk.org; Ananyev, Konstantin <konstantin.ananyev at intel.com>;
> Richardson, Bruce <bruce.richardson at intel.com>; De Lara Guarch, Pablo
> <pablo.de.lara.guarch at intel.com>
> Subject: Re: [PATCH 2/6] testpmd: configurable tx_first burst number
> 
> 2016-05-05 18:46, Zhihong Wang:
> > This patch enables configurable tx_first burst number.
> >
> > Use "start tx_first (burst_num)" to specify how many bursts of packets to
> > be sent before forwarding start, or "start tx_first" like before for the
> > default 1 burst send.
> 
> The idea here is to fill the loopback latency gap with bursts.
> Would it be possible to make it automatic by detecting the first
> received packets to stop Tx generator?

The idea is great! The implementation might not be graceful though
-- current tx_first mode first calls txonly engine before calling the
actual engine, say iofwd, so iofwd is not established before tx_first
is done, therefore no detection.

It's possible to do this, but we need to implement another forward
engine like "io_retry_fill_first" alone, it complicates testpmd just for
this loop back test.

Looks to me it's better to use combination of existing fwd engines to
do this, it's also more flexible with burst number parameters.