> On 9/28/2020 8:31 AM, Dumitru Ceara wrote: > > On 9/22/20 4:21 PM, Ferruh Yigit wrote: > >> On 9/18/2020 11:36 AM, Dumitru Ceara wrote: > >>> Even though ring interfaces don't support any other TX/RX offloads they > >>> do support sending multi segment packets and this should be advertised > >>> in order to not break applications that use ring interfaces. > >>> > >> > >> Does ring PMD support sending multi segmented packets? > >> > > > > Yes, sending multi segmented packets works fine with ring PMD. > > > > Define "works fine" :) > > All PMDs can put the first mbuf of the chained mbuf to the ring, in that case > what is the difference between the ones supports 'DEV_TX_OFFLOAD_MULTI_SEGS' > and > the ones doesn't support? > > If the traffic is only from ring PMD to ring PMD, you won't recognize the > difference between segmented or not-segmented mbufs, and it will look like > segmented packets works fine. > But if there is other PMDs involved in the forwarding, or if need to process > the > packets, will it still work fine? > > >> As far as I can see ring PMD doesn't know about the mbuf segments. > >> > > > > Right, the PMD doesn't care about the mbuf segments but it implicitly > > supports sending multi segmented packets. From what I see it's actually > > the case for most of the PMDs, in the sense that most don't even check > > the DEV_TX_OFFLOAD_MULTI_SEGS flag and if the application sends multi > > segment packets they are just accepted. > > > > As far as I can see, if the segmented packets sent, the ring PMD will put the > first mbuf into the ring without doing anything specific to the next segments. > > If the 'DEV_TX_OFFLOAD_MULTI_SEGS' is supported I expect it should detect the > segmented packets and put each chained mbuf into the separate field in the > ring.
Hmm, wonder why do you think this is necessary? From my perspective current behaviour is sufficient for TX-ing multi-seg packets over the ring. > > > > > However, the fact that the ring PMD doesn't advertise this implicit > > support forces applications that use ring PMD to have a special case for > > handling ring interfaces. If the ring PMD would advertise > > DEV_TX_OFFLOAD_MULTI_SEGS this would allow upper layers to be oblivious > > to the type of underlying interface. > > > > This is not handling the special case for the ring PMD, this is why he have > the > offload capability flag. Application should behave according capability flags, > not per specific PMD. > > Is there any specific usecase you are trying to cover?
