News for hackers. Stuff that matters.

A comment on Http2 explained. Parent comment

Re:Http2 explained by getsat on Thursday February 12, 2015 @10:12PM (#9042702)
Linux starts to act weird around 200,000 concurrent connections in my experience, even with aggressive sysctl tuning. You end up with weird edge cases like netstat literally taking 15 minutes of CPU time (in kernel) before it dumps the list of connections to stdout.

Not sure about FreeBSD or any other OSes.

[ Parent | on HN ]
Re:Http2 explained by btmorex on Friday February 13, 2015 @07:36AM (#9043994)
Not saying netstat isn't slow, but:

# time sh -c 'netstat -tn | wc -l' 486206

real 0m13.538s user 0m1.698s sys 0m10.380s

It still works with a whole lost of connections. (in fairness, only about 130k were connected)

[ Parent | on HN ]
Re:Http2 explained by getsat on Saturday February 14, 2015 @06:49PM (#9051181)
The problem is that it doesn't scale linearly. There's some O(n4) algorithm being used in netstat or some kernel syscalls or something. Once you go over 250k, things get _really_ weird.
[ Parent | on HN ]
Re:Http2 explained by patrickmcmanus on Sunday February 15, 2015 @09:55AM (#9052732)
try ss -nt instead.. it uses netlink sockets instead of /proc and generally scales much better
[ Parent | on HN ]
Re:Http2 explained by getsat on Monday February 16, 2015 @09:23PM (#9060341)
Thanks for the tip!
[ Parent | on HN ]