Ethernet slowdown problem

Jason Gunthorpe (jgg@ualberta.ca)
Fri, 9 Jul 1999 11:07:16 -0600 (MDT)


I just got hit by that weird ethernet slowdown problem that some people
have reported, here is the results of a ping over ethernet:

--- blue.priv.deltatee.com ping statistics ---
1165 packets transmitted, 1159 packets received, 0% packet loss
round-trip min/avg/max = 1796.0/4706.5/7994.9 ms

The very odd part is that telnet sessions out of this machine are very
responsive still - I am typing this message over telnet. The nfs client is
-extremely- slow and so is the (user land) NFS server that this machine
runs. DNS has also become quite slow.

I fired up tcpdump on my DNS server and did a lookup, here is the trace:

10:56:51.387148 172.16.1.131.1035 > 172.16.1.1.53: 9218+ (29)
10:56:51.387148 172.16.1.1.53 > 172.16.1.131.1035: 9218 NXDomain* 0/1/0
(102)
10:56:54.386925 172.16.1.131.1035 > 172.16.1.2.53: 9218+ (29)
10:56:54.396925 172.16.1.2.53 > 172.16.1.131.1035: 9218 NXDomain* 0/1/0
(102)

I also straced the 'host' command and noticed that it sent a total of 4
messages using send and in this instance it wasn't able to recieve any
messages, it reported a DNS timeout error.

The kernel is 2.2.10 with no patches, the network card is a Tulip using
the tulip driver (Dlink DE-530):

tulip.c:v0.89H 5/23/98 becker@cesdis.gsfc.nasa.gov
eth0: Digital DC21041 Tulip at 0x6400, 21041 mode, 00 80 c8 7d e6 28, IRQ 10.
eth0:21041 Media information at 30, default media 0800 (Autosense).
eth0: 21041 media #0, 10baseT.
eth0: 21041 media #0, 10baseT.
eth0: 21041 media #0, 10baseT.

Hrm, just as I finished writing this the problem went away (which I have
never seen it do before).

Hope this helps,
Jason

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