Lowering DEBUG process for less CPU I/O

Unanswered Question
Jun 16th, 2007

Does anyone know about a command that can lower the DEBUG process at the IOS so that it doesn't jam the CPU?

I have this problem too.
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Paolo Bevilacqua Sat, 06/16/2007 - 09:03

The main limiting factor when doing debugs is that debug is sent to console port and terminal moonitor, tha can be slow. So disable that with "no loggign console" and "no logging monito", and log debug instead to a memory buffer "logging buffer".

Richard Burts Sat, 06/16/2007 - 11:53


I do not know of any command which will lower the debug process. I do agree with Paolo about the impact of debug output sent to the console, and agree less about the impact of sending debug to terminal monitor. The single best thing you can do to minimize the impact of debug is to prevent debug output from going to the console.

I would take a slightly different approach than Paolo in preventing debug output to the console. His approach will work, but I think it may be a bit drastic to stop all logging to the console. I would suggest setting the logging level of the console to informational, which will stop debug output but still allow other output.

There are several factors which contribute to the impact of debug output being sent to the console: 1) the console usually operates at 9600 and 2) output to the console generates a CPU interrupt per character of output. Neither of these factors are present in output to terminal monitor. Terminal monitor usually is operating at network link speed and this output generates a CPU interrupt per line (much less impact than per character). I would agree that not sending debug output to terminal monitor would reduce SOME overhead. But I doubt that it is very significant.



royalblues Sun, 06/17/2007 - 00:17


Debug processes are genreally CPU intensive and i agree with Rick and Paolo that not logging them to console would slightly alleviate the problem.

What you should try most of the times when you debug, is to limit the debug by configuring an access-list around the problem and associating it with the debug.

for eg.. the debug ip packet details would generally crash your router if it has considerable amount of traffic(i saw an 38xx ISR stopped responding to this command). instaead i would use something like this

debug ip packet detail 100 where 100 would reference an access-list which associates with the problem you are trying to troubleshoot

HTH, rate if it does



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