Ilya Maximets <i.maximets@xxxxxxx> writes: > On 11/22/22 15:03, Aaron Conole wrote: >> When processing upcall commands, two groups of data are available to >> userspace for processing: the actual packet data and the kernel >> sw flow key data. The inclusion of the flow key allows the userspace >> avoid running through the dissection again. >> >> However, the userspace can choose to ignore the flow key data, as is >> the case in some ovs-vswitchd upcall processing. For these messages, >> having the flow key data merely adds additional data to the upcall >> pipeline without any actual gain. Userspace simply throws the data >> away anyway. > > Hi, Aaron. While it's true that OVS in userpsace is re-parsing the > packet from scratch and using the newly parsed key for the OpenFlow > translation, the kernel-porvided key is still used in a few important > places. Mainly for the compatibility checking. The use is described > here in more details: > https://docs.kernel.org/networking/openvswitch.html#flow-key-compatibility > > We need to compare the key generated in userspace with the key > generated by the kernel to know if it's safe to install the new flow > to the kernel, i.e. if the kernel and OVS userpsace are parsing the > packet in the same way. > > On the other hand, OVS today doesn't check the data, it only checks > which fields are present. So, if we can generate and pass the bitmap > of fields present in the key or something similar without sending the > full key, that might still save some CPU cycles and memory in the > socket buffer while preserving the ability to check for forward and > backward compatibility. What do you think? Maybe that can work. I will try testing. If so, then I would change this semantic to send just the bitmap rather than omitting everything. > The rest of the patch set seems useful even without patch #1 though. I agree - but I didn't know if it made sense to submit the series without adding something impactful (like a test). I will work a bit more on the flow area - maybe I can add enough actions and matches to implement basic flow tests to submit while we think more about the feature. > Nit: This patch #1 should probably be merged with the patch #6 and be > at the end of a patch set, so the selftest and the main code are updated > at the same time. Okay - I can restructure them this way. > Best regards, Ilya Maximets.
