Jon Kohler wrote: > > > > On May 7, 2025, at 4:43 PM, Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx> wrote: > > > > !-------------------------------------------------------------------| > > CAUTION: External Email > > > > |-------------------------------------------------------------------! > > > > Jon Kohler wrote: > >> Hoist rcu_dereference(tun->xdp_prog) out of tun_xdp_one, so that > >> rcu_deference is called once during batch processing. > > > > I'm skeptical that this does anything. > > > > The compiler can inline tun_xdp_one and indeed seems to do so. And > > then it can cache the read in a register if that is the best use of > > a register. > > The thought here is that if a compiler decided to not-inline tun_xdp_one > (perhaps it grew to big, or the compiler was being sassy), that the intent > would simply be that this wants to be called once-and-only-once. This > change just makes that intent more clear, and is a nice little cleanup. > > I’ve got a series that stacks on top of this that enables multi-buffer support > and I can keep an eye on if that gets inlined or not. That will only give you one outcome with a specific compiler, platform and build configuration. I would just drop this and let the compiler handle such optimizations.
