It appears from further research that both process and fast switching interrupt the CPU. The difference is that with process switching, during the interrupt, the CPU determines the type of packet and copies it into processor memory if necessary (this decision is platform dependent). Finally, the processor places the packet on the appropriate process' input queue and the interrupt is released.
The next time the scheduler runs, it notes the packet in the input queue of ip_input (assuming it was an IP packet), and schedules this process to run. With fast switching, the CPU is interrupted, and the packet is actually switched at that time. This is according to the article here: http://www.cisco.com/warp/public/105/20.html There's also more info in this article: http://www.cisco.com/warp/public/63/queue_drops.html However, I wasn't able to glean an answer to the original question about the second part of the statisitic when you do a show interface. Do you think the second part (the interrupt part) is just refering to the second situation (switching the packet during the CPU interrupt)? Perhaps that book you mentioned answers the question. Thanks. Priscilla M.C. van den Bovenkamp wrote: > > Priscilla Oppenheimer wrote: > > > Some processing supposedly should take place without causing > a CPU > > interrupt. For example, fast switching, if you can believe > some > > descriptions, doesn't interrupt the CPU. > > > > Perhaps a high usage consumed by interrupts implies that a > lot of traffic > > isn't being fast switched (or express forwarded). > > > > I can't say for sure though. > > IIRC, it's exactly the other way around. CPU used within > interrrupts is > traffic being fastswitched, where the entire packet I/O is done > in the > interrupt handlers. > > Process switching lots of traffic would show up as the 'IP > Input' > (assuming it's IP traffic) process eating lots of CPU. > > (Perhaps I should re-read 'Inside Cisco IOS Software > Architecture'...) > > Regards, > > Marco. > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=50072&t=49954 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
