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Beginner

Prioritize process when CPU usage is close to 100%

Hello,

I would like to know if there is a way to prioritize some process over others when CPU usage is close to 100%.

For instance, prioritize BGP or PPP processes so that WAN connectivity is not lost during peak CPU usage.

 

Thank you.

Thomas.

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7 REPLIES 7
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VIP Engager

Re: Prioritize process when CPU usage is close to 100%

 

 - That is not supported on CIsco switches. You will need to tackle the problem , if possible or buy more performant hardware (if that is the cause).

 M.

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Beginner

Re: Prioritize process when CPU usage is close to 100%

Thank you for your reply. Any idea if it's supported on Cisco routers?

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VIP Engager

Re: Prioritize process when CPU usage is close to 100%

 

 - Nope.

    M.

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VIP Expert

Re: Prioritize process when CPU usage is close to 100%

On switches, "normal" traffic forwarding should often be little impacted by high CPU because the data plane is supported by ASICs.

On routers, Cisco already, I believe, assigns priorities to processes, so "more important" processes should get 1st dibs on the CPU. Further, for "normal" traffic forwarding, it takes place in the "interrupt" process, so that too generally gets priority access to the CPU.

That said, way back when there was a set of scheduler config commands (see https://www.cisco.com/c/en/us/td/docs/ios/fundamentals/command/reference/cf_book/cf_r1.html, search for "scheduler allocate"). I doubt these commands are supported on newer platforms.
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Beginner

Re: Prioritize process when CPU usage is close to 100%

Hello Joseph,

Thank you for your reply.

 

I tried to overload a C1111-8P in my lab by sending a lot of small packets and unfortunately I lost BGP peering with my neighbor.

So it seems that, by default, there is no mechanism to prioritize BGP process. Or, maybe, I push the test too far by sending too much packets...

 

I will try to play with the command scheduler and see if notice some improvements:

#scheduler ?  
  heapcheck         Extra checking to validate memory
  interval          Maximum interval before running lowest priority process
  max-sched-time    Maximum time scheduler can run without flagging an error
  max-task-time     Maximum time that a task can run without flagging an error
  process-watchdog  Action for looping processes
  run-degraded      Continue running as long as possible.
  runtime           Process runtime controls
  timercheck        Extra checking to validate timer

Thomas

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VIP Expert

Re: Prioritize process when CPU usage is close to 100%

Was your test on the same or different interface used by BGP?

Ah, surprised to see scheduler commands sill present.
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Beginner

Re: Prioritize process when CPU usage is close to 100%

Hello,

It was on another interface.

BGP peering was using gi0/0/0 interface and traffic was between gi0/1/0 and gi0/1/1 interfaces.