Interrupts and Exceptions

1. TODO 1 in irqtop_starter.c: read the header line; count "CPU" with strstr → ncpu
2. TODO 2: for each line: the id before ':', the sum of up to ncpu numbers (strtoull), the name
3. TODO 3: match lines of the two snapshots by id (strcmp); count = after − before
4. TODO 4: qsort by count, biggest first; print the top 10
5. Run it idle; then type, copy a big file, run yes > /dev/null: which lines change?

reference, real

$ ./irqtop          # test machine, idle
   IRQ  per second  name
   LOC          92  Local timer interrupts
   CAL          25  Function call interrupts
    49           3  … virtio7-input.0
$ ./irqtop 6        # while reading files
   IRQ  per second  name
    37         138  … virtio1-req.0
   LOC          92  Local timer interrupts
   CAL          26  Function call interrupts
$ ./irqtop          # QEMU guest, dd
    25         493  … virtio0-req.0
   LOC         351  Local timer interrupts

Careful: the lines ERR and MIS have only ONE number, not one per CPU. strtoull tells you when it found no number: end == p.