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

[David Rientjes <rientjes@google.com>]

On Wed, 10 Apr 2013, 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.
> 
> 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.
> 

CONFIG_NUMA_BALANCING should be default n on everything, but probably for 
unknown reasons: ARCH_WANT_NUMA_VARIABLE_LOCALITY isn't default n and 
nothing on x86 actually disables it.

> Cc: mgorman@suse.de
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
>  mm/mempolicy.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 7431001..8a4dc29 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2530,8 +2530,8 @@ static void __init check_numabalancing_enable(void)
>  		numabalancing_default = true;
>  
>  	if (nr_node_ids > 1 && !numabalancing_override) {
> -		printk(KERN_INFO "Enabling automatic NUMA balancing. "
> -			"Configure with numa_balancing= or sysctl");
> +		pr_info("Enabling automatic NUMA balancing.\n");
> +		pr_info("Change with numa_balancing= or echo -NUMA >/sys/kernel/debug/sched_features\n");
>  		set_numabalancing_state(numabalancing_default);
>  	}
>  }

Shouldn't this be echo NO_NUMA?

/sys/kernel/debug/sched_features only exists for CONFIG_SCHED_DEBUG, so
perhaps suppress this pointer for configs where it's not helpful?

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