scheduler allocate command. Tunning for performance

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Oct 29th, 2007
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Hi all,

although I've seen suggestions against modifying the default values for this command, I've come across a situation in which it seems to help a lot to increase the parameter "interrupt-time" associated with fast switching.

Basically, although the overall CPU util (on a 7200 w NPE-G1), is not exceeding 8% under this particular traffic profile the router drops packets when a "show run", "show ver" or "wr mem" commands are issued. The profile is roughly 100Mbps of unidirectional traffic, from which 30Mbps are packets of 128 bytes in size.

If I increase the mentioned parameter, there are no droped packets. However I'm conscious of the implications this could have with some other processes (i.e. routing protocols)

Few related questions:

How can we determine/calculate the right tunning of both values associated with the scheduler allocate command?

How can we relate this to the documentation which mentions "network interrupt contexts"? (Does this mean a single interrupt?)

How can this optimisation be related to traffic profiles? (i.e. interrupt time vs. packet rates, sizes, buffers, etc)


Thanks

Hector Hernandez

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aghaznavi Fri, 11/02/2007 - 13:53
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configure the scheduler interval 500 command; this schedules low priority processes to run every 500 ms. This provides time for you to run some commands, even if CPU usage is at 100 percent. On Cisco 7200 and Cisco 7500 series routers, issue the scheduler allocate 3000 1000 command.


Use the show processes cpu command to check if CPU utilization is high due to interrupts or processes.

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