Introduction
High CPU is one of the most common symptom observed by users when troubleshooting some issue with WAAS. High CPU in WAAS could be because of some geniune reason and as such this should not cause any problem. If high CPU stays for a long period of time, more investigation is required to get to the root cause of the issue.
Troubleshooting High CPU
Check the following for understanding the cause of high CPU
Determine the process causing High CPU
Use command such as: show process cpu | ex 0.0 to pick on process that uses any CPU time. Follow the link for more info on this.
http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a00804916e0.shtml
Determine Traffic that is Punted
This will list packets that are software switched instead of hardware. Follow the link for more info on this.
http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a00804916e0.shtml#utilities
Determine if CPU Utilization is due to Interrupts
This will show if any CPU Interrupts are responsible for high CPU. Follow the link for more info.
http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a00800a70f2.shtml#high_cpu
Determine if CPU Utilization is due to ACLs
This will show if any ACL is using too much processing leading to high CPU. Follow the link for more info.
http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a00804916e0.shtml#oal
Profiling
Profiling is used for determining what is causing the issue. Here is an example from a profiling used for determining high cpu cause (from a BGP based Example):
a) Run a "show region". Take special note of the "Start" address for the "main:text" region. For example..
Test#show region
Region Manager:
Start End Size(b) Class Media Name
0x60008BD8 0x6191C1F4 26293789 IText R/O main:text
++++
In this command output the "start" is 60008BD8 and the "end" is 6191C1F4.
b) Next turn on "profile" by configuring the following: profile 60008BD8 6191C1F4 10
In this case 60008BD8 would be the start of main:text address and 6191C1F4 would be the end of main:text. The 10 represents the rate of granularity that the profiling needs to be configured at. You would run the above command for about 3 minutes.
c) Next start the "profile" by configuring "profile start" and let this run for 10 mins the "profile stop"
d) Turn off the "more" page scrolling feature as you would be collecting large info by the following config: "term len 0"
e) Collect the "CPU" profile info by configuring:
show profile ter
show profile detail
Note: The above info would be lengthy and you would want to set the logging.
f) Finally enter the following commands:
clear profile
unprofile all
Check the output data to understand what is causing the issue.
Related Information
Cisco WAAS Troubleshooting Guide for Release 4.1.3 and Later
