linux-kernel - Re: [patch] mm, show_mem: suppress page counts in non-blockable contexts

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Message-ID: <alpine.DEB.2.02.1302271410230.7155@chino.kir.corp.google.com>
Date:	Wed, 27 Feb 2013 14:13:37 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, show_mem: suppress page counts in non-blockable
 contexts

On Wed, 27 Feb 2013, Dave Hansen wrote:

> On 02/26/2013 04:46 PM, David Rientjes wrote:
> > diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> > --- a/arch/arm/mm/init.c
> > +++ b/arch/arm/mm/init.c
> > @@ -99,6 +99,9 @@ void show_mem(unsigned int filter)
> >  	printk("Mem-info:\n");
> >  	show_free_areas(filter);
> > 
> > +	if (filter & SHOW_MEM_FILTER_PAGE_COUNT)
> > +		return;
> > +
> 
> Won't this just look like a funky truncated warning to the end user?
> 

No, because of the uninhibited call to show_free_areas() above.  This 
still dumps the pcp state, global and per-node page type breakdown, and 
free pages at given order.  The only things suppresses are the total 
pages, pages reserved, pages shared, and pages non-shared counts that are 
quite expensive to determine because it walks all memory while irqs are 
disabled and increases with the amount of RAM a system has.
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