Linux 2.2.x problem

From: Peter Zaitsev (pz@spylog.ru)
Date: Mon Jun 19 2000 - 08:15:01 EST


I have the following problem using linux.
My system running linux 2.2.15aa2 (The problem presists with other resent kernels) on dual PIII system. system has Intel EtherExpress100 card, but I don't thing this should be the real problem....

The system gets many connections in a time - about 250-300 per second.

Often it works quite healthy - 20% user + 20% system + 60% idle and sometimes I see the system CPU usage is extremely hi: 70% and up.

The number of active sockets during this is not to huge:

[root@titan dem]# netstat -nt | wc -l
  17116

But the number of sockets in SYN_RECV state is relatively huge:

[root@titan dem]# netstat -nt | grep SYN_RECV | wc -l
   3405

Therefore then the systems operates normaly the number of sockets in this state is much smaller:
[root@titan dem]# netstat -nt | grep SYN_RECV | wc -l
     37
This number raises up to 100-300 sometimes but not thousands.

Any ideas why may this be ?

P.S: I previosely changed tcp_max_syn_backlog to 4096 instead of default 128 and additionaly changed ip_local_ports to 32768 61000

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