CPU utilization query

Experts,


Core-Switch#sh processes cpu so 1
CPU utilization for five seconds: 40%/1%; one minute: 35%; five minutes: 35%
 PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
  30   5248799482118370040        247 19.51% 16.34% 16.71%   0 Cat4k Mgmt LoPri
  29  20503967322395826272          0 12.95% 12.54% 12.48%   0 Cat4k Mgmt HiPri
  52   424438104 753203851        563  2.79%  2.51%  2.48%   0 Spanning Tree
  58   339416368 752979472        450  0.87%  0.68%  0.65%   0 IP Input
  18   105731420 236879115        446  1.19%  0.59%  0.54%   0 ARP Input
 119    30336808 296249983        102  0.31%  0.28%  0.29%   0 HSRP (Standby)
 136         456       595        766  0.23%  0.25%  0.11%   1 SSH Process
 117    25561340   4205501       6078  0.95%  0.22%  0.06%   0 SpanTree Flush
  73    25176580  74544113        337  0.15%  0.17%  0.15%   0 CEF: IPv4 proces
   5    77307312   7631624      10129  0.00%  0.13%  0.16%   0 Check heaps
  60     8963520 120836284         74  0.07%  0.12%  0.11%   0 CDP Protocol
 102     4048480 648058463          6  0.07%  0.07%  0.07%   0 PM Callback
  28    18581940   1187792      15644  0.00%  0.04%  0.00%   0 Per-minute Jobs
  40     2467048  11026359        223  0.07%  0.04%  0.05%   0 Compute load avg
  27     6981148  48482600        143  0.00%  0.04%  0.05%   0 Per-Second Jobs
 123    28174196  16539707       1703  0.00%  0.04%  0.05%   0 SNMP ENGINE
  53     2513132  87421476         28  0.00%  0.02%  0.00%   0 DTP Protocol

Can you please help me understand this results.

What is CPU utilization for five seconds: 40%/1%?

Comments


  • Can you please help me understand this results.

    What is CPU utilization for five seconds: 40%/1%?

    Hi Krishna,

    It's CPU utilization percent for the last five seconds. The second number is CPU interrupt percent. 

    According to Cisco documentation, its normal for the interrupt percentage to be greater than 0 percent and less than 5 percent. It is acceptable for the interrupt percentage to be between 5 percent and 10 percent. An interrupt percentage over 10 percent should be investigated.

    Hope this helps!

  • 40%, tells how busy the CPU was in the past 5 seconds. This number is the total CPU utilization for all the active system processes, including the percentage of time at the interrupt level.

    1%, shows the percentage of time at the interrupt level in the past 5 seconds. The interrupt percentage is the CPU time spent receiving packets from the switch hardware. The percentage of time at interrupt level is always less than or equal to the total CPU utilization.

     

    http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/troubleshooting/cpu_util.html

  • peetypeety ✭✭✭

    What is CPU utilization for five seconds: 40%/1%?

    What others have left out is the magic 39%: the device spent 39% of CPU handling packets via CEF (i.e. non-interrupt-based packet forwarding).  I got this result by calculating 40% - 1% = 39%, if it wasn't otherwise obvious.

  • Hi Peety,

    If CEF is non-interrupt-based packet forwarding, then what is interrupt-based packet forwarding?

  • peetypeety ✭✭✭

    Legacy packet forwarding, which includes "process switching" (every inbound packet requires the router to "walk" the routing table to find the best match) and "fast-cache switching" (every inbound packet checks the routing cache for recent matches; if one is found, it's used, otherwise the router "walks" the routing table to find a match AND populates the routing cache with that information; cache entries are aged out after five minutes).

  • Prcoess switching is one of them.

    EDIT

    Peety has given better explanation.

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