High cpu utilization specifically related to TTY?

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Apr 7th, 2009
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I've run into an issue where I've seen the cpu utilization spike specifically

relating to the TTY Daemon?? Any Suggestions? - Thanks

0000-00#sh proc cpu sort

CPU utilization for five seconds: 26%/2%; one minute: 24%; five minutes: 30%

PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process

47 749085132-1499372249 0 23.92% 21.82% 27.82% 5 TTY Daemon

44 27375532 11236279 2436 0.57% 0.48% 0.39% 0 IP Input

110 6637416 9586137 692 0.24% 0.25% 0.22% 0 Crypto PAS Proc

13 159600 255928 623 0.08% 0.02% 0.00% 0 ARP Input

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drolemc Mon, 04/13/2009 - 13:46
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The TTY Background process is a generic process used by all terminal lines (console, aux, async, and so on). Normally there should not be any impact on the performance of the router since this process has a lower priority compared to the other processes that need to be scheduled by the Cisco IOS software. If this process takes high CPU utilization, check whether "logging synchronous" is configured under "line con 0." The possible cause could be CSCed16920

lamav Mon, 04/13/2009 - 16:26
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I experienced this before, and it involved a known bug in the IOS. I upgraded the IOS and all was fixed.



Richard Burts Mon, 04/13/2009 - 19:50
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While the impact of generating log/syslog messages to the logging buffer or to the terminal monitor is pretty low, the impact of generating log messages to the console can get pretty high. If the TTY process is generating high CPU I would suggest that you might look for any of these:

- is there any debug running which might be sending output to the console? what does show debug indicate?

- are there access lists which use the log parameter and might be generating volumes of output to the console?

- if you connect to the console port, is there much output scrolling on the screen? what kind of output is it? are there ways to reduce the volume of console output?




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