[dpdk-dev] Which counters are set by rte_eth_stats_get

[Tom Barbette <barbette@kth.se>]

Hi ethdev maintainers,


Support of drivers for the fields in rte_eth_stats is a bit random, and never mentioned in the doc. A quick survey showed me :


ipackets : implemented by all drivers
ibytes : all except null, ring
ierror : all except af_packet, ark, avf, axgbe, fm10k, kni, null, pcap, ring, szedata2, vhost
imissed : *only* af_packet, avp, axgbe, fm10k, kni, liquidio, mlx4, mlx5, null, pcap, ring, szedata2, tap, vhost, virtio
rx_nombuf : *only* bnx2x,bnxt,bonding,ena,enic,failsafe,mlx4,mlx5,netvsc,nfp,qede,szedata2,tap,virtio

With no way to know if we can rely on the value or not, as a DPDK user pov. The only way to know if we can rely on a given counter is to grep the driver code. Except if I missed something?

Also the doc of rte_eth_stats_get only mention io packets, bytes and errors. Not the other fields, and the way it is written let the reader think it is always supported if the function does not return 0.

I can update the doc to reflect the state of things. But maybe we could make that function return a bitmask which tells which counter has been set. But that would break the ABI... We could also have the bitmask set through a passed pointer, so it does not break code checking the return value is 0. Or maybe have the bitmask elsewhere, like for the offloads? Which fields are supported is probably a constant. So that may make more sense.

If you give me directions, I can propose a patch.

Cheers,
Tom