[Crash-utility] crash vs irqs

[Dave Anderson]

D. Hugh Redelmeier wrote:
> Now that the irq command appears to work, I notice that it is too
> verbose.
> 
> On my machine (AMD Athlon x2), it unconditionally prints 2304 structs,
> each taking 27 lines.  Of those, only 23 appear to have been used in
> the day that the machine had been up.
> 
> Is there a simple way to print only the used entries or perhaps only
> print an entry if it is different from the one before it?
> 
> Does that kind of logic exist for printing other tables?  If not,
> would it be useful?

Wow -- until fairly recently the NR_IRQS definition has been a
relatively small number, and on most architectures it still is.
I don't think there are any other commands that print such
verbose output for a table containing that many structures
where most of them are unused.

I suppose if it's obvious that an IRQ index is not in use, it's output
could be shortened, or maybe a new option could be added that only
prints out "used" entries.  I await your patch suggestion...

> 
> 
> I wonder why the kernel allocates so many irq_desc entries.  According
> to "nm -f sysv vmlinux", irq_desc is 294912 bytes -- more than the
> whole RAM on the first UNIX machine I used.
>

Amazing isn't it?

> 
> I was looking at x86_64.c: x86_64_dump_irq.  Its last line says:
>         error(FATAL, "ia64_dump_irq: irq_desc[] does not exist?\n");
> It should say:
>         error(FATAL, "x86_64_dump_irq: irq_desc[] does not exist?\n");
> 

Thanks -- I'll fix that...

Dave