Re: [Crash-utility] [PATCH 0/3] Add a "percpu" command
----- Original Message -----
On Tue, 15 Oct 2013 14:20:08 -0400 (EDT)
Dave Anderson <anderson(a)redhat.com> wrote:
> ----- Original Message -----
> > On Sat, 12 Oct 2013 21:41:49 +0200
> > Petr Tesarik <ptesarik(a)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.
How about the somewhat similar usage for "p", where the self-identified object
could also contain a per-cpu symbol:
<per-cpu symbol>:<cpu-identifier>
Then we could do something like:
crash> p <per-cpu symbol>
which would continue to output the type and addresses as it does now,
but then alternatively you could:
crash> p <per-cpu symbol>:<cpu_identifier>
which would just print the datatype contents for the cpus specified?
Dave