> From: Stephen Hemminger [mailto:step...@networkplumber.org] > Sent: Wednesday, 1 May 2024 18.45 > > On Wed, 1 May 2024 17:25:59 +0100 > Ferruh Yigit <ferruh.yi...@amd.com> wrote: > > > > - Remove the tx_error counter since it was not correct. > > > When transmit ring is full it is not an error and > > > the driver correctly returns only the number sent. > > > > > > > nack > > Transmit full is not only return case here. > > There are actual errors continue to process relying this error > calculation. > > Also there are error cases like interface down. > > Those error cases should be handled individually if we remove this. > > I suggest split this change to separate patch. > > I see multiple drivers have copy/pasted same code and consider > transmit full as an error. It is not.
+1 Transmit full is certainly not an error! > > There should be a new statistic at ethdev layer that does record > transmit full, and make it across all drivers, but that would have > to wait for ABI change. What happens to these non-transmittable packets depend on the application. Our application discards them and count them in a (per-port, per-queue) application level counter tx_nodescr, which eventually becomes IF-MIB::ifOutDiscards in SNMP. I think many applications behave similarly, so having an ethdev layer tx_nodescr counter might be helpful. Other applications could try to retransmit them; if there are still no TX descriptors, they will be counted again. In case anyone gets funny ideas: The PMD should still not free those non-transmitted packet mbufs, because the application might want to treat them differently than the transmitted packets, e.g. for latency stats or packet capture.
