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SubjectNetwork slow-downs
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Date
Hello, 

I am experiencing quite drastically slow-downs on the network
performance on a dual P-II system running kernel 2.2.10.

The machine currently has two network cards, one ISA NE2000 clone and
one Intel Ether Express 100 card, which is the card I have trouble
with. The machine works many as NFS-server.

After upgrading to the 2.2 series we have from time to time
experienced severe slow-downs on the TCP performance, down to 1-10% of
the normal performance, measured by ttcp. According to /proc/net/dev,
we have no packet loss when the network slows down.

When using ping from an Ultra 2 running Solaris 2.6, I record an
average ping response ranging from 100 to 4000 milliseconds, but no
loss, the ping response is just slow.

The performance goes back to normal when I take down the interface and
reinsert the eepro100 module into the kernel. After I've done that,
the performance is fine for a couple of days or maybe weeks.

I have tried to just take the interface down with ifconfig without
removing the module, and this seems to fix the problem, but only until
a large file is read through NFS. (I'm using the user level nfsd, but
I have had this problem using knfsd too.)

When I measure the ping response while dd-ing a 60 MB file to
/dev/null through NFS on another machine, the response seems to be
fine until the whole file has been read, then the ping response grows
rapidly up to about an average of 100-200 ms, and after a hour or so
we end up with an average response of 3000-4000 ms.

The traffic that goes through the NE2000-card seems to be unaffected
by what's happening on the eepro100 interface, the ping response is
stable way below 5 ms all time. I used to have an Accton 21140-based
card instead of the eepro100 card, and I experienced the same problems
using that card too.

I have had seen this problem in 2.2.6, 2.2.7, 2.2.9 and 2.2.10.

We have another box which is used as a workstation, but no SMP, and I
have on one occasion seen this problem there, and this box does not
have a SMP enabled kernel.

I am not yet able to find a way to reproduce the problem, but I have
noticed that it somehow seems to be triggered by messing with the nfs
daemon (killing and restarting it, that is).

I hope this is a problem that could be fixed, and I'll be happy to
provide more details, and otherwise do whatever is needed to find out
what's happening.

--
Øystein Svendsen


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