Re: [PATCH 1/8] numa: add generic percpu var numa_node_id() implementation

On Fri, 2010-04-16 at 13:33 -0700, Andrew Morton wrote:
> On Thu, 15 Apr 2010 13:29:56 -0400
> Lee Schermerhorn <[email protected]> wrote:
> 
> > Rework the generic version of the numa_node_id() function to use the
> > new generic percpu variable infrastructure.
> > 
> > Guard the new implementation with a new config option:
> > 
> >         CONFIG_USE_PERCPU_NUMA_NODE_ID.
> > 
> > Archs which support this new implemention will default this option
> > to 'y' when NUMA is configured.  This config option could be removed
> > if/when all archs switch over to the generic percpu implementation
> > of numa_node_id().  Arch support involves:
> > 
> >   1) converting any existing per cpu variable implementations to use
> >      this implementation.  x86_64 is an instance of such an arch.
> >   2) archs that don't use a per cpu variable for numa_node_id() will
> >      need to initialize the new per cpu variable "numa_node" as cpus
> >      are brought on-line.  ia64 is an example.
> >   3) Defining USE_PERCPU_NUMA_NODE_ID in arch dependent Kconfig--e.g.,
> >      when NUMA is configured.  This is required because I have
> >      retained the old implementation by default to allow archs to
> >      be modified incrementally, as desired.
> > 
> > Subsequent patches will convert x86_64 and ia64 to use this
> > implemenation.
> 
> So which arches _aren't_ converted?  powerpc, sparc and alpha?

Right.  Plus ARM, mips, ...

I could take a cut at other archs, but can't test them.  I'm hoping that
this patch doesn't break the existing implementation for them.  It
should be a no-op until the new support is enabled via Kconfig.  The
fact that both x86_64 and ia64 build with just this patch gives me some
hope but not a lot of confidence.

I see that you've merged the series with into -mm.  We'll see what
happens.  Of course, no reports of errors could just mean no testing.

> 
> Is there sufficient info here for the maintainers to be able to
> perform the conversion with minimal head-scratching?

Arch maintainers will need to chime in on that.  I'd hoped that the list
above and the examples of x86_64 and ia64 in the subsequent patches
would suffice.

Lee