Re: [RFC PATCH] powerpc/numa: add ability to disable and debug topology updates

On Mon, 2014-09-15 at 16:54 -0700, Nishanth Aravamudan wrote:

On 15.09.2014 [15:05:36 +1000], Michael Ellerman wrote:

quoted

On Tue, 2014-09-09 at 13:09 -0700, Nishanth Aravamudan wrote:

quoted

Does it really need to be a boot param, or could it be a debugfs or
sysctl flag? ie. do we need to disable it immediately at boot or would
it be OK if it was /etc/rc.local or similar that turned it off ?

We need it off at boot, potentially. An LPAR does not indicate that it
will or will not respond to the events in any synchronous fashion, so
the hypervisor is free to send them to us whenever.

OK. I guess we're stuck with a boot time parameter for on/off then.

quoted

As far as the debug goes, we could just use pr_debug() with
CONFIG_DYNAMIC_DEBUG, it's not quite as easy to enable as a kernel
parameter but for the odd bit of debugging it should be fine.

That's a good point, I wonder with that mechanism if we should perhaps
extend/remove other static debugging methods in favor of that (e.g.,
numa=debug)?

Yes definitely.

It's slightly more arcane to enable, ie. to turn on dynamic debugging in numa.c
at boot your command line needs:

  dyndbg="file numa.c +p"

But that's fine unless it's an option you expect users to be using regularly
which none of these are.

cheers