On 5/7/2024 5:00 PM, Morten Brørup wrote: >> 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. >
I am against ehtdev layer being aware of SW drivers and behave differently for them. This is dev_ops and can be managed per driver. We can add helper functions for drivers if there is a common pattern. >> >> 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. >
