On Sat, Jul 13, 2024 at 9:34 PM Jakub Kicinski <kuba@xxxxxxxxxx> wrote: > > On Sat, 13 Jul 2024 12:23:31 +0530 Srivats P wrote: > > I'm seeing a behaviour difference between kernel 5.4 and 5.15 wrt the > > AF_XDP queues used for zero copy. This is specific to the mlx5. > > > > Assume you have 'n' queues configured on the interface. > > > > In 5.4, you had to use n to 2*n -1 queue numbers for AF_XDP zc. Using > > 0 to n-1 queues would use copy mode. > > > > In 5.15, you have to use 0 to n-1 for zero copy also. Socket creation > > fails if you use queue >=n. > > > > Also, with 5.4 netdev stats would not be incremented for AF_XDP > > packets whereas with 5.15 they do get incremented? > > > > Can someone confirm this behaviour change or point me to relevant > > mailing list discussions or some other information on the same? My > > google-fu is failing me. > > > > When did this change go into the kernel? I can't find anything in the > > kernelnewbies.org changelog between 5.4 and 5.15. > > Hm, can't find the relevant commit quickly either now. But it's > intentional. The new behavior is how all other drivers work. > Hopefully this change isn't a deal breaker for anyone because > long term the lack of uniformity among drivers is a PITA. Matching how other drivers behave is a good thing. As an application developer however I need to support both kernel versions. So I'm trying to find out when this change happened so that I can add a kernel version check in the code to modify the behaviour for mellanox drivers. As a developer/user visible change in behaviour, things like these need more visibility. Information about XDP and AF_XDP is unfortunately spread around too much. It would be really useful for application developers if we could consolidate the information at one place like DPDK does. Srivats
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