How to monitor Linux UDP buffer available space?

Question

I have a java app on linux which opens UDP socket and waits for messages.

After couple of hours under heavy load, there is a packet loss, i.e. the packets are receiv

Answer 1

rx_queue will tell you the queue length at any given instant, but it will not tell you how full the queue has been, i.e. the highwater mark. There is no way to constantly monitor this value, and no way to get it programmatically (see How do I get amount of queued data for UDP socket?).

The only way I can imagine monitoring the queue length is to move the queue into your own program. In other words, start two threads -- one is reading the socket as fast as it can and dumping the datagrams into your queue; and the other one is your program pulling from this queue and processing the packets. This of course assumes that you can assure each thread is on a separate CPU. Now you can monitor the length of your own queue and keep track of the highwater mark.