netisr kernel thread gone wild ?

[Michael BUTOW]

Hello all,

I am observing a strange problem where the netisr kernel thread goes from nearly no CPU to using nearly 100%.

At roughly the same time, the amount of wired pages on the system increases, first slowly (+100 pages/sec), then faster and faster (maybe 400-500 pages/sec).

Looking with vmstat shows that only the malloc pages are increasing - the rest of the wired pages remain stable.

The collect tool showed the network interface at 5% bandwidth utilisation (it's 10MB half-duplex, tu card), so it appears not that much.

The CPU was fully utilised, at first roughly 60% user and 40% system, but the system load increased slowly to 100% (netisr).

Does anybody have an explanation for the behaviour of the netisr thread and the seeming correlation to the increase in malloc pages ?

I would also appreciate any hints to the further diagnosis of the problem. So far we have used ps to identify the kernel thread.
We also twice forced a crash and analysed the kernel core file. In both cases we got:

(dbx) pd vm_page_free_count
0
(dbx) pd vm_perfsum.vpf_freepages
0

We tried the VM tuning recommended in http://groups.google.de/group/fa.alpha-osf-managers/attach/6fc7d8d1ac927a1d/v40d-tune.html?part=2 .

However, this did not fix the problem of netisr.

I can provide /etc/sysconfigtab if it helps.

Looking forward to any suggestions,
Michael Bütow

[Al Licause]

Which version of Tru64unix and which patch kit are you running ?

[Michael BUTOW]

This problem was seen on Tru64 4.0F + PK7.