May be off topic : System CPU usage

[Punj, Arun]

[ Please cc: [e-mail] ]

Folks

I am running into a curious problem on linux 2.4.20 kernel. 

The problem :

  Every 25 minutes the sytem usage as indicated by "top -i -d 1" 
  goes up from 0 to about 50% and stays at this level for around 
  100 seconds and than comes down to zero or near zero again. 
  The user cpu % stays at 0. And the CPU used by all the active 
  process put togather stays below 5%

  The system is idle when this happens in so far as I can tell. 
  The only tasks which show up in the top are :
    -- "X" and [ CPU usage ~ 5%]
    -- top itself [ CPU usage ~ 0%]

  The hardware configuration is as follows:
    P4 2.4Ghz 512M Ram, 128M IDE compatible Flash Drive, 
    there is a 50 Meg CramFs parition on flash and 200 M
    ext3 partition.

Could this be a kernel configuration issue.

Any help would be greatly appreciate.

thanks
Arun Punj

A snippet of what top looks like when this happens, observe the system
usage:
----------------------------------------------------------------------------

  8:59am  up 1 day, 22:21,  5 users,  load average: 0.56, 0.49, 0.46
79 processes: 74 sleeping, 4 running, 0 zombie, 1 stopped
CPU states: 1.7% user,  48.9% system,  0.0% nice, 49.4% idle
Mem:   506380K av,  217256K used,  289124K free,       0K shrd,   15976K
buff
Swap:       0K av,       0K used,       0K free                   88928K
cached

  PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME COMMAND
  712 root      17  -1  142M  13M  2620 R <   4.9  2.7 209:28 X
 7917 root       9   0  1100 1100   876 R     0.0  0.2   0:00 top
 
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