linux-kernel - Re: [PATCH] mm: numa: Initialse numa balancing after jump label initialisation

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Date:	Tue, 28 Jan 2014 08:49:11 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: numa: Initialse numa balancing after jump label
 initialisation

On Mon, Jan 27, 2014 at 02:43:36PM -0800, Andrew Morton wrote:
> On Mon, 27 Jan 2014 15:51:27 +0000 Mel Gorman <mgorman@...e.de> wrote:
> 
> > The command line parsing takes place before jump labels are initialised which
> > generates a warning if numa_balancing= is specified and CONFIG_JUMP_LABEL
> > is set. On older kernls before commit c4b2c0c5 (static_key: WARN on
> > usage before jump_label_init was called) the kernel would have crashed.
> > This patch enables automatic numa balancing later in the initialisation
> > process if numa_balancing= is specified.
> > 
> > ...
> >
> > @@ -2666,9 +2666,14 @@ static void __init check_numabalancing_enable(void)
> >  	if (IS_ENABLED(CONFIG_NUMA_BALANCING_DEFAULT_ENABLED))
> >  		numabalancing_default = true;
> >  
> > +	/* Parsed by setup_numabalancing. override == 1 enables, -1 disables */
> > +	if (numabalancing_override)
> > +		set_numabalancing_state(numabalancing_override == 1);
> > +
> >  	if (nr_node_ids > 1 && !numabalancing_override) {
> > -		printk(KERN_INFO "Enabling automatic NUMA balancing. "
> > -			"Configure with numa_balancing= or sysctl");
> > +		printk(KERN_INFO "%s automatic NUMA balancing. "
> > +			"Configure with numa_balancing= or sysctl",
> > +			numabalancing_default ? "Enabling" : "Disabling");
> >  		set_numabalancing_state(numabalancing_default);
> >  	}
> >  }
> 
> Current mainline is a bit different from this:
> 
> 		printk(KERN_INFO "Enabling automatic NUMA balancing. "
> 			"Configure with numa_balancing= or the kernel.numa_balancing sysctl");
> 
> So this won't apply as-is to -stable.
> 

That's ok.

> I assume you suggested the -stable backport to fix the
> it-crashes-before-c4b2c0c5 thing, so it isn't really needed in 3.12.x.
> 

I am recommending this patch for -stable because 3.12.x crashes. c4b2c0c5
prevents a crash but it is still the case that the parameter is not handled
properly so backporting c4b2c0c5 is not a suitable alternative.

> Or something.  Please sort all that out when Greg comes back with
> a hey-that-didnt-apply.

I will.

-- 
Mel Gorman
SUSE Labs
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