CPU Utilisation does not addup to total CPU %

Answered Question

Hi, My 1760 router do have VPN hardware module, without it, CPU was high and encryption process too much of the CPU, now after we install VPN module, there is no cpu % for encryption process, but my question is sum of the CPU % is much much lower than the total CPU %, what are the hidden processes taking all these CPU


HHRTR01#sh proc cpu | ex 0.00
CPU utilization for five seconds: 15%/11%; one minute: 16%; five minutes: 18%
PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
   5      145439      9297      15643  1.06%  0.22%  0.18%   0 Check heaps
  50        2312       473       4887  2.12%  0.56%  0.25%   6 SSH Process
  51       69168     50055       1381  0.24%  0.18%  0.19%   0 IP Input

Correct Answer by xabrouck about 7 years 6 months ago

Hi,


0.16%+0.57% = 0.73%

0.73% rounded = 1%

Total CPU utilization = 35%

CPU utilization under interrupt = 34%

CPU utilization in processes = 35%-34% = 1% = 0.73% rounded


You can't see what's happening under interrupt ('show stacks' gives you the amount of network/timer/... interrupts but it's not very useful).

Usually, what happens under interrupt is the traffic forwarding using CEF.


So, at first sight, there's nothing to worry about on your router. It's a bit busy forwarding packets.


If you need to troubleshoot the CPU utilization under interrupt, you will need to do profiling with the assistance of a TAC engineer who has the ability to decode the profiling results.


hope this helps,

X.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Loading.
xabrouck Wed, 12/02/2009 - 06:31
User Badges:
  • Cisco Employee,

The 15% include the 11% of CPU usage under interrupt. The sum of 5-sec CPU usage of all processes should give you 15%-11%=4%.


Total CPU utilization = CPU utilization in processes + CPU utilization in interrupt.


X.

Hi, Thanks for reply but it doesnt make sense to me , look below 5sec total is less than 1%, any way how can I chk interupt CPU utilisation.


PHTHRTR01#sh proc cpu | ex 0.00
CPU utilization for five seconds: 35%/34%; one minute: 41%; five minutes: 36%
PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
  51      126074     81191       1552  0.16%  0.28%  0.21%   0 IP Input
  54       11119      1667       6670  0.57%  4.19%  1.96%   6 SSH Process

Hi ,


Thank for reply,


But it dosn't make sense to me, 5sec total is less than 1% but total is above 30%, any way how could I chk interupt CPU utilisation,


This router having prblem with hanging when IPSec traffic or WAN link utilisation goes high


PHTHRTR01#sh proc cpu | ex 0.00
CPU utilization for five seconds: 35%/34%; one minute: 41%; five minutes: 36%
PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
  51      126074     81191       1552  0.16%  0.28%  0.21%   0 IP Input
  54       11119      1667       6670  0.57%  4.19%  1.96%   6 SSH Process

Correct Answer
xabrouck Thu, 12/03/2009 - 23:27
User Badges:
  • Cisco Employee,

Hi,


0.16%+0.57% = 0.73%

0.73% rounded = 1%

Total CPU utilization = 35%

CPU utilization under interrupt = 34%

CPU utilization in processes = 35%-34% = 1% = 0.73% rounded


You can't see what's happening under interrupt ('show stacks' gives you the amount of network/timer/... interrupts but it's not very useful).

Usually, what happens under interrupt is the traffic forwarding using CEF.


So, at first sight, there's nothing to worry about on your router. It's a bit busy forwarding packets.


If you need to troubleshoot the CPU utilization under interrupt, you will need to do profiling with the assistance of a TAC engineer who has the ability to decode the profiling results.


hope this helps,

X.

Actions

This Discussion