linux-kernel - Re: [PATCH v3 3/3] slub: min order when debug_guardpage

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Message-ID: <20111208073316.GA2402@redhat.com>
Date:	Thu, 8 Dec 2011 08:33:17 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [PATCH v3 3/3] slub: min order when debug_guardpage_minorder > 0

On Wed, Dec 07, 2011 at 02:07:55PM -0800, David Rientjes wrote:
> On Fri, 18 Nov 2011, Stanislaw Gruszka wrote:
> 
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 7d2a996..a66be56 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -3645,6 +3645,9 @@ void __init kmem_cache_init(void)
> >  	struct kmem_cache *temp_kmem_cache_node;
> >  	unsigned long kmalloc_size;
> >  
> > +	if (debug_guardpage_minorder())
> > +		slub_max_order = 0;
> > +
> >  	kmem_size = offsetof(struct kmem_cache, node) +
> >  				nr_node_ids * sizeof(struct kmem_cache_node *);
> > 
> 
> I'd recommend at least printing a warning about why slub_max_order was 
> reduced because users may be concerned why they can't now change any 
> cache's order with /sys/kernel/slab/cache/order.

It's only happen with debug_guardpage_minorder=N parameter, so
perhaps I'll just document that in kernel-parameters.txt

Thanks
Stanislaw
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