[c-nsp] no scheduler max-sched-time

[Jeff Chambers]

Thanks for this excellent info.

Should I assume that "no scheduler max-sched-time" is
configured by default on routers running 12.2(25)S1
and that the configuration of "service internal"
simply causes it to show up in the running configuration?


Also, is the following interpretation correct?
"no scheduler max-sched-time" should only affect
the reporting of a CPU Hog via log/syslog messages
and not actually increase the chance that a CPU
will hang due to a CPU Hog.


Jeff Chambers


-----Original Message-----
From: Bruce Pinsky [mailto:bep at whack.org]
Sent: Monday, November 29, 2004 3:47 PM
To: Jeff Chambers
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] no scheduler max-sched-time


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Jeff Chambers wrote:
| I noticed the following command configured on a Cisco
| 7206VXR router that was recently upgraded to 12.2(25)S1.
|
| "no scheduler max-sched-time"
|
|
| The CLI gives me the following help information.
|
| Router(config)#scheduler ?
|   max-sched-time    Maximum time scheduler can run without flagging an
error
|

There is no formal public documentation that I can find.  However, this
command comes from the introduction of a new CPU HOG (scheduler watchdog)
reporting mechanism that was introduced into 12.2S (as well as 12.0S and
12.2T).  Prior to this new mechanism, CPU HOG's were only reported after a
process would suspend. This is less useful because it does not indicate
where most of the time is being spent to cause the CPU HOG. With the
introduction of the enhancement, a CPU HOG is reported at the moment it
crosses the defined threshold.  The command is used to changed the default
maximum threshold.  Setting the maximum to zero or using the explicit "no"
version of the command disables the capability.

|
| This command only shows up in the configuration if
| "service internal" is configured.  I can't find any
| documentation for the "no scheduler max-sched-time"
| command.  Can anyone point me in the right direction?
|
| I'm mainly curious if this command is harmless or not.
| After reading bug ID CSCdw61805, it appears leaving
| "service internal" configured on a production router
| might be a bad idea by itself.
|

"service internal" does expose a number of commands that can have negative
effects on system operation if used improperly.  This is usually the
motivation for obscuring them with this mode of the parser.  The fact that
most are undocumented is unfortunate because it leaves people to guess at
both what the command does and how detrimental it may or may not be.  There
is a push inside of cisco to eliminate and prevent undocumented commands
going forward, but I can't say when or if the old ones might get done.

- --
=========
bep

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