Well, let us use pidentd and a tool ibench to measure its performance. It is 30 requests per second here. Nothing to test, it is too slow. OK, let us patch pidentd with patch from directory Patches. After this it handles about 4300 requests per second and becomes handy tool to pollute socket tables with lots of timewait buckets.
So, each test starts from pollution tables with 30000 sockets and then doing full dump of the table piped to wc and measuring timings with time:
Results:
No comments. Though one comment is necessary, most of time without tcp_diag is wasted inside kernel with completely blocked networking. More than 10 seconds, yes. tcp_diag does the same work for 100 milliseconds of system time.