Hi Zoltan, > -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Zoltan Kiss > Sent: Friday, March 18, 2016 1:33 PM > To: Lu, Wenzhuo; Wu, Jingjing; dev at dpdk.org > Subject: Re: [dpdk-dev] ixgbe TX function selection > > > > On 18/03/16 00:45, Lu, Wenzhuo wrote: > > Hi Zoltan, > > > > > >> -----Original Message----- > >> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Zoltan Kiss > >> Sent: Friday, March 18, 2016 1:11 AM > >> To: Wu, Jingjing; dev at dpdk.org > >> Subject: Re: [dpdk-dev] ixgbe TX function selection > >> > >> > >> > >> On 10/03/16 07:51, Wu, Jingjing wrote: > >>> Hi, Zoltan > >>> > >>>> -----Original Message----- > >>>> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Zoltan Kiss > >>>> Sent: Wednesday, March 2, 2016 3:19 AM > >>>> To: dev at dpdk.org > >>>> Subject: [dpdk-dev] ixgbe TX function selection > >>>> > >>>> Hi, > >>>> > >>>> I've noticed that ixgbe_set_tx_function() selects the non-SG function > >>>> even if (dev->data->scattered_rx == 1). That seems a bit dangerous, > >>>> as you can turn that on inadvertently when you don't set > >>>> max_rx_pkt_len and buffer size in certain ways. I've learnt it in the > >>>> hard way, as my segmented packets were leaking memory on the TX path, > >>>> which doesn't cries if you send out segmented packets. > >>>> How should this case be treated? Assert on the non-SG TX side for the > >>>> 'next' pointer? Or turning on SG if RX has it? It doesn't seem to be > >>>> a solid way as other interfaces still can have SG turned on. > >>>> > >>> > >>> If you look into the ixgbe_set_tx_function, you will find tx function > >>> selection is decided by the tx_flags on queue configure, which is > >>> passed by rte_eth_txconf. So even you set dev->data->scattered_rx to > >>> 1, if the tx_flags is ETH_TXQ_FLAGS_NOMULTSEGS, ixgbe_xmit_pkts_simple > >>> is still selected as tx function. So, you'd better to set tx_flags=0, and > >>> have a try. > >> > >> You mean getting default_txconf from rte_eth_dev_info_get() and explicitly > >> turn > >> ETH_TXQ_FLAGS_NOMULTSEGS to 0? (filling tx_flags with zeros doesn't work > >> very well) That's a way to solve it for me, but I'm rather talking about > >> using > >> defaults which doesn't cause memory leak quite easily. > > Yes, ETH_TXQ_FLAGS_NOMULTSEGS only can be set to 1 when you know all your > > packets will not be segmented. > > I think that means normally we should use full function path for TX, for we > > have no knowledge about if the packets will be > segmented or not. > > You don't need to set tx_flags to 0, only the ETH_TXQ_FLAGS_NOMULTSEGS bit > > should be 0, the other bits can be 1 if needed. > > So can we agree that the default settings should set > ETH_TXQ_FLAGS_NOMULTSEGS to 0?
I'd prefer to keep things as they are right now. There always will be arguments and supporters for both alternatives: Should the fastest or the most comprehensive path be the default one. Again default txq_flags can vary from one PMD to another. So, I think the right behaviour for the app would be not to rely on default value but set it up manually to the desired value. Konstantin > > > > > >> > >>> > >>>> Regards, > >>>> > >>>> Zoltan