[Crash-utility] [PATCH 0/3] Add a "percpu" command

[Petr Tesarik]

On Tue, 15 Oct 2013 14:20:08 -0400 (EDT)
Dave Anderson <anderson at redhat.com> wrote:

> ----- Original Message -----
> > On Sat, 12 Oct 2013 21:41:49 +0200
> > Petr Tesarik <ptesarik at suse.cz> wrote:
> > 
> > >[...]
> > > In general, I think it's a matter of taste, and if you dislike new
> > > commands, it all boils down to finding a suitable syntax to extend the
> > > existing commands. Unfortunately, "-c" (as CPU) is already taken for
> > > count, and "-p" (as processor) is already taken for pointer
> > > dereference. :-(
> > > 
> > > I can think of:
> > > 
> > > A. "-C" (but it requires a shift key, and two options that only
> > >    differ in case may be confusing)
> > > B. any other random letter ("-a" is free).
> > 
> > Hm, it seems this is the only blocking piece. If nobody has an idea
> > until tomorrow, I'll just pick '-C', even though I hate both the shift
> > key and the fact that another command ('irq') uses a different option
> > ('-c') for the same concept.
> 
> I agree with you on both counts.  
> 
> I haven't had the chance to reply to your second response (I took the holiday
> off yesterday), but I think a suitable compromise would be to change the 
> "struct/union/* -c count" option to perhaps a "-n number" option?  
> 
> Another other option that crossed my mind would be to have a unique manner
> for presenting per-cpu addresses and cpu(s) as a command argument.  They are
> offset values, but they could be confused for zero-based kernel virtual address
> arches (s390/s390x), so there would need to be a option to differentiate
> zero-based kernel virtual addresses, and then a second option of the cpu
> specifier.    

FYI I went through the same exercise...

> But anyway, maybe per-cpu addresses could be made to be "self-identified"
> if they were presented as "<offset>:<cpu-identifer>", where the colon would
> define the argument as a per-cpu item, and the <cpu-identifier> part could be
> one of the following:
> 
>   offset:               nothing following the colon means the current cpu
>   offset:a              all cpus
>   offset:cpu-specifier  same as your patch or the irq command

This is genius! I really love this syntax and I'm working on the patch
already.

Petr T