On Tue, 2023-03-28 at 01:16 -0700, Eric Dumazet wrote: > > About visibility: Even before 'drop reasons' developers can always use > the call graph . > > perf record -a -g -e skb:kfree_skb ... Yeah, except right now it doesn't work in mac80211 because we have these "RX handlers" that just return a status, and then a single place drops the skb. > Really drop reasons are nice when you want filtering and convenience. > But they are a lot of work to add/maintain. > This all comes at a cost (both maintenance but also run time cost > because we need to propagate reasons ) Right ... I don't think the runtime cost would be much of an issue here (we just get them as a return value from one function to pass to kfree_skb), but the maintenance is hard. I guess we could also restructure the code to call kfree_skb() in all those places that want drop it and then we have the call trace, but I doubt that would actually be cheaper both in the maintenance sense (always need to pay attention to it) or in the runtime sense. johannes
