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

[Mel Gorman <mgorman@suse.de>]

On Wed, Apr 10, 2013 at 12:35:14PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
> 
> When the "default y" CONFIG_NUMA_BALANCING_DEFAULT_ENABLED is enabled,
> the message it prints refers to a sysctl to disable it again.
> But that sysctl doesn't exist.
> 

True.

> Document the correct (highly obscure method) through debugfs.
> 
> This should be also in Documentation/* but isn't.
> 
> Also fix the checkpatch problems.
> 
> BTW I think the "default y" is highly dubious for such a
> experimential feature.
> 

As David pointed out, CONFIG_NUMA_BALANCING_DEFAULT_ENABLED only comes
into play when CONFIG_NUMA_BALANCING is set and CONFIG_NUMA_BALANCING
will default to N for make oldconfig. I think it's sensible to enable it
by default if it's configured in.

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

printk(KERN_INFO "Enabling automatic NUMA balancing. "
	"Configure with numa_balancing="
#ifdef CONFIG_SCHED_DEBUG
	" or echo [NO_]NUMA > /sys/kernel/debug/sched_features"
#endif
	".\n");

-- 
Mel Gorman
SUSE Labs

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