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Date: Tue, 6 Feb 2007 21:44:14 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hugh@veritas.com>, Paul Mundt <lethal@linux-sh.org>,
       Christoph Lameter <clameter@sgi.com>, linux-kernel@vger.kernel.org
Subject: Re: [patch 2/3] smaps: add pages referenced count to smaps
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On Tue, 6 Feb 2007 21:27:03 -0800 (PST) David Rientjes <rientjes@google.com> wrote:

> @@ -190,18 +191,20 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats
>  
>  	if (mss)
>  		seq_printf(m,
> -			   "Size:          %8lu kB\n"
> -			   "Rss:           %8lu kB\n"
> -			   "Shared_Clean:  %8lu kB\n"
> -			   "Shared_Dirty:  %8lu kB\n"
> -			   "Private_Clean: %8lu kB\n"
> -			   "Private_Dirty: %8lu kB\n",
> +			   "Size:           %8lu kB\n"
> +			   "Rss:            %8lu kB\n"
> +			   "Shared_Clean:   %8lu kB\n"
> +			   "Shared_Dirty:   %8lu kB\n"
> +			   "Private_Clean:  %8lu kB\n"
> +			   "Private_Dirty:  %8lu kB\n"
> +			   "Pgs_Referenced: %8li\n",

I guess we might as well make this %8lu kB as well?

>  			   (vma->vm_end - vma->vm_start) >> 10,
>  			   mss->resident >> 10,
>  			   mss->shared_clean  >> 10,
>  			   mss->shared_dirty  >> 10,
>  			   mss->private_clean >> 10,
> -			   mss->private_dirty >> 10);
> +			   mss->private_dirty >> 10,
> +			   mss->referenced);
>
> ...
>
> +	/* Accumulate the number of pages that have been accessed. */
> +	if (PageReferenced(page))
> +		mss->referenced++;

This is testing the software-referenced bit.  We want to be counting the
pte-referenced bits (pte_young).

Hence poking clear_refs should run pte_mkold().

Perhaps we should also be running ClearPageReferenced and counting pages
which are pte_young()||PageReferenced.