[c-nsp] 3550 High CPU - nothing in proc cpu

[Hector Herrera]

I had another opportunity to debug the high cpu usage on the 3550-12t.

show proc cpu indicated that cpu load was 39% interrupt, 40% total

So it's definitively a high interrupt rate that is using up the cpu.

I also debugged the switching mechanism, and although I have high
amounts of TTL-expired events, they only occur at a rate of 2-3 per
second.

I proceeded to profile the cpu usage with:

profile <start> <end> <granularity>
profile start
... 10 mins later
profile stop
show profile terse

Granularity was 8 due to the largest free block being about half the
size of the main:text section.

This gave me a listing of all the memory ranges and a count of how
many times the cpu was found to be in that memory location.

System Total     = 000141506
Interrupt Total  = 000056163 (39 percent)
Sched Total      = 000094547 (66 percent)

Interrupt [00] = 000056163 (39 percent)

The interrupt breakdown is (top 3):

0x475F50 with 3281 counts (~5.4 per sec.)
0x4B82B8 with 1667 counts (~2.7 per sec)
0x4B8F90 with 1456 counts (~2.4 per sec)

My question is:

How do I convert those memory addresses into something that would tell
me what interrupts are being triggered so much?

Thank you,

Hector