> From: Stephen Hemminger [mailto:step...@networkplumber.org] > Sent: Tuesday, 7 May 2024 16.51
> I would prefer that the SW statistics be handled generically by ethdev > layers and used by all such drivers. I agree. Please note that maintaining counters in the ethdev layer might cause more cache misses than maintaining them in the hot parts of the individual drivers' data structures, so it's not all that simple. ;-) Until then, let's find a short term solution, viable to implement across all software NIC drivers without API/ABI breakage. > > The most complete version of SW stats now is in the virtio driver. It looks like the virtio PMD maintains the counters; they are not retrieved from the host. Considering a DPDK application running as a virtual machine (guest) on a host server... If the host is unable to put a packet onto the guest's virtio RX queue - like when a HW NIC is out of RX descriptors - is it counted somewhere visible to the guest? Similarly, if the guest is unable to put a packet onto its virtio TX queue, is it counted somewhere visible to the host? > If reset needs to be reliable (debatable), then it needs to be done without > atomics. Let's modify that slightly: Without performance degradation in the fast path. I'm not sure that all atomic operations are slow. But you are right that it needs to be done without _Atomic counters; they seem to be slow.
