On Mon, 2017-03-13 at 18:34 -0500, Josh Hunt wrote: > In this particular case they really do want to know total # of bytes in > the receive queue, not the data bytes they can consume from an > application pov. The kernel currently only exposes this value through > netlink or /proc/net/udp from what I saw. > > I believe Eric's suggestion in his previous mail was to export all of > these meminfo metrics via a single socket option call similar to how its > done in netlink. We could then use that for both call sites. > > I agree that it would be useful to also have the data you and Eric are > suggesting exposed somewhere, the total # of skb->len bytes sitting in > the receive queue. I could add that as a second socket option.
Please note that UDP stack does not maintain a per socket sum(skb->len) Implementing this in a system call would require to lock the receive queue (blocking BH) and iterating over a potential huge skb list. Or add a new socket field and add/sub every skb->len of packets added/removed to/from receive queue. So I would prefer to not provide this information, this looks quite a bloat.
