On Sep 2, 12:44pm, Alex Bligh wrote:
> Subject: Re: [nsp] show proc cpu
> Rephrase:
>
> > > Anyone know what Cisco's are doing when the CPU usage column in
> > > show proc cpu adds up to nothing like the number at the top? Debugging
> > > normally does this, but it isn't switched on in this case (4700).
> > > I think it's switching packets that does it, though I thought that
> > > normally hit IP Input.
> > ...
> > > telehouse16#show proc cpu
> > > CPU utilization for five seconds: 37%/35%; one minute: 42%; five minutes:
41%
> >
> > Notice the 35%? That's the time spent at interrupt level. So the usage
> > from show proc cpu is only expected to add up to around 2%.
>
> OK, I have a router spending 35% of its time at interrupt level. On a
> 4700 what processes take up interrupt level time. I'm not process switching
> as that (I believe) turns up as IP input. So is the the interrupt overhead
> of Fast Switching (for instance)?
>
Yes. I know my note wasn't that clear:
+> "fast switching" (ie. "ip route-cache") as well as CEF ....
+> .... Also flow switching.
These are among the packet forwarding schemes which hit the
interrupt-level CPU.
Tony
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