> -----Original Message----- > From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com] > Sent: Wednesday, March 9, 2016 16:27 > To: Ananyev, Konstantin <konstantin.ananyev at intel.com> > Cc: Kulasek, TomaszX <tomaszx.kulasek at intel.com>; dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v2 1/2] ethdev: add buffered tx api > > 2016-03-09 15:23, Ananyev, Konstantin: > > > > > > 2016-03-09 13:36, Ananyev, Konstantin: > > > > > > + if (to_send == 0) > > > > > > + return 0; > > > > > > > > > > Why this check is done in the lib? > > > > > What is the performance gain if we are idle? > > > > > It can be done outside if needed. > > > > > > > > Yes, that could be done outside, but if user has to do it anyway, > > > > why not to put it inside? > > > > I don't expect any performance gain/loss because of that - just > > > > seems a bit more convenient to the user. > > > > > > It is handling an idle case so there is no gain obviously. > > > But the condition branching is surely a loss. > > > > I suppose that condition should always be checked: > > either in user code prior to function call or inside the function call > > itself. > > So don't expect any difference in performance here... > > Do you have any particular example when you think it would? > > Or are you talking about rte_eth_tx_buffer() calling > > rte_eth_tx_buffer_flush() internally? > > For that one - both are flush is 'static inline' , so I expect > > compiler be smart enough to remove this redundant check. > > > > > So why the user would you like to do this check? > > Just for user convenience - to save him doing that manually. > > Probably I've missed something. If we remove this check, the function will > do nothing, right? How is it changing the behaviour?
If we remove this check, function will try to send 0 packets and check condition for error. So we gain nothing with removing that. Tomasz
