[...]

quoted

+	TP_ARGS(map_id, processed, sched, xdp_stats),
 
 	TP_STRUCT__entry(
 		__field(int, map_id)
 		__field(u32, act)
 		__field(int, cpu)
-		__field(unsigned int, drops)
 		__field(unsigned int, processed)

So, struct member @processed will takeover the room for @drops.

Can you please test how an old xdp_monitor program will react to this?
Will it fail, or extract and show wrong values?

Ack, right. I think we should keep the struct layout in order to maintain
back-compatibility. I will fix it in v4.

The xdp_mointor tool is in several external git repos:

 https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/samples/bpf/xdp_monitor_kern.c
 https://github.com/xdp-project/xdp-tutorial/tree/master/tracing02-xdp-monitor

Do you have any plans for fixing those tools?

I update xdp_monitor_{kern,user}.c and xdp_redirect_cpu_{kern,user}.c in the
patch. Do you mean to post a dedicated patch for xdp-project tutorial?

Regards,
Lorenzo

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer