'top' showing high interrupt rate

[Paul Hamilton]

Hi,

I noticed that top shows a rather high interrupt rate, usually hovering
around 60%!  Here is a sample:-

last pid:  2879;  load averages:  0.34,  0.24,  0.18
up 1+17:26:56  17:18:10
36 processes:  2 running, 33 sleeping, 1 zombie
CPU states:  0.6% user,  0.0% nice,  0.0% system, 59.8% interrupt, 39.6%
idle
Mem: 11M Active, 5072K Inact, 7988K Wired, 3552K Cache, 6480K Buf, 960K Free
Swap: 128M Total, 4608K Used, 123M Free, 3% Inuse

  PID USERNAME      PRI NICE  SIZE    RES STATE    TIME   WCPU    CPU
COMMAND
  135 root           10   0   980K   528K nanslp  11:38  0.00%  0.00% cron
  201 root            2   0  2824K  1132K select   3:46  0.00%  0.00% ppp
  108 root            2   0   452K   208K select   0:29  0.00%  0.00% natd
  127 root            2   0  2760K  1704K select   0:14  0.00%  0.00% named
  223 root            2   0  2068K   908K select   0:10  0.00%  0.00% sshd
  212 root            2   0  2044K   876K select   0:10  0.00%  0.00% sshd
<snip>

pstat -T says:

	120/1064 files
	4M/127M swap space

vmstat 10 says:


 procs      memory      page                    disks     faults      cpu
 r b w     avm    fre  flt  re  pi  po  fr  sr ad0 ad1   in   sy  cs us sy
id
 0 0 0   12992   4992    1   0   0   0   1   0   0   0  237   52   8  0 59
41
 0 0 0    9404   4992    1   0   0   0   0   0   0   0  229   35   6  0 60
40
 0 0 0   15572   4868   16   0   0   0   7   0   0   0  231  938  10  1 61
38
 0 0 0   17820   4868    8   0   0   0   0   0   1   0  230   45   8  0 60
40
 0 0 0   12492   5224    8   0   0   0   9   0   0   0  231   47   8  1 60
39

dmesg says:

Copyright (c) 1992-2000 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD 4.2-RELEASE #1: Tue Feb 13 22:51:23 WST 2001
    root at ant.compwest.net.au:/usr/src/sys/compile/ANT
Timecounter "i8254"  frequency 1193182 Hz
CPU: Pentium/P55C (165.79-MHz 586-class CPU)
  Origin = "GenuineIntel"  Id = 0x544  Stepping = 4
  Features=0x8001bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,MMX>
real memory  = 33554432 (32768K bytes)
avail memory = 29478912 (28788K bytes)

Yes, the server only has 32MB or RAM, however, it's only using 4MB of VM.

Anyone have any idea how to troubleshoot further?  How can I isolate what is
causing the rather high interrupt rate?

Cheers,

Paul Hamilton