Re: [PATCH] mm: Print the correct method to disable automatic numa migration

[Mel Gorman <mgorman@suse.de>]

On Thu, Apr 11, 2013 at 08:53:04AM -0700, Andi Kleen wrote:
> > > > David has also already pointed out the problems with NO_NUMA vs -NUMA and
> > > > the fact that the option only exists if CONFIG_SCHED_DEBUG which I agree
> > > > is unfortunate. Ends up with this sort of mess
> > > 
> > > We just need the sysctl. Are you adding one or should I send
> > > another patch with it?
> > > 
> > 
> > I hadn't planned on it in the short term at least. Originally there was
> 
> I'll send a patch.
> 

Ok.

> But are you taking care of the documentation of all the existing knobs?
> 

Which knobs? The sched_features knobs? No, I was not planning on
documenting them. Some of them are already partially documented in
kernel/sched/features.h but the consequences of tuning them is heavily
workload dependant. While this is unsatisfactory, the interface is only
intended for debugging. For NUMA balancing, the tuning knob is a kernel
parameter and it is already documented in Documentation/kernel-parameters.txt

> I think if you had done that earlier you would have noticed
> that the current situation is not very satisfying.
> 
> Writing documentation is one of the best ways we have
> to sanitize user interfaces.
> 
> > revisited NUMA balancing a long time ago but too many bugs have been
> > getting in the way.
> 
> That will likely make everything even worse.
> 

With one exception, the bugs I've been working on are not related to
automatic NUMA balancing.

-- 
Mel Gorman
SUSE Labs

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