Basic question about "sh proc cpu"

[henrybb]

CPU utilization for five seconds: 5%/2%; one minute: 3%; five minutes: 2%

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

1 1736 58 29931 0% 0% 0% 0 Check heaps

2 68 585 116 1.00% 1.00% 0% 0 IP Input

I don't know 1.00% of IP Input is included in which part of "five seconds: 5%/2%". 5% or 2% ?

I read description of "sh proc cpu" on command reference, but I don't know whether cpu time spent by "ip input" is belong to CPU time spent at the interrupt level.

"ip input" do process swithing but it need interrupt,too. So I am in doubt whether cpu time of "interrupt level" on last 5 seconds include "ip input" or just include interrupt time for "ip input".

Does cpu time of "interrupt level" include all type swithing,for example,process swithing and CEF swithing,etc ?

What mean of "interrupt level" ? Does it mean all of interrupt ? Included interrupt for process switching but exclude cpu time of "ip input" process.

Except swiching interrupt, any other interrupt type ?

thanks!

[pkhatri · Accepted solution]

Hi,

"IP Input" is included in the non-interrupt part of the CPU utilisation. In your example, that would be the 5% portion of the output.

The "IP Input" process is scheduled as part of the normal multi-tasking operation of the CPU. There is no interrupt associated with IP Input. That is one of the major reasons why process-switching is bad for you. Fast switching (for connections already cached) and CEF switching result in a CPU interrupt as soon as a packet arrives whereas process switched packets have to wait until the CPU decides to schedule the IP Input process.

Hope that helps.

Pls do remember to rate posts.

Paresh

[henrybb]

thanks!

I edited post. And there is another question.

What mean of "interrupt level" ? Does it mean all of interrupt ? Included interrupt for "ip input" but exclude cpu time of "ip input" process.

Except swiching interrupt, any other interrupt type ?

[pkhatri · Accepted solution]

Henry,

The percentage of CPU time spent by the interrupt handle routines is included in the interrupt time. And no, this does not include 'IP Input, because as I mentioned earlier, that is not interrupt-driven.

There could be all sorts of reasons there is an interrupt that the CPU has to handle. There's interrupts when the CPU has to send out routing update packets, SNMP packets etc...

Henry, it would be really nice if you rated the posts of people who take the time to respond to your questions.. that would be very much appreciated.

Paresh