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Date: Mon, 12 Jun 2006 09:43:17 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
To: Rohit Seth <rohitseth@google.com>
cc: Andrew Morton <akpm@osdl.org>, Linux-mm@kvack.org,
       Linux-kernel@vger.kernel.org
Subject: Re: [PATCH]: Adding a counter in vma to indicate the number of
 physical pages backing it
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On Fri, 9 Jun 2006, Rohit Seth wrote:

> There is currently /proc/<pid>/smaps that prints the detailed
> information about the usage of physical pages but that is a very
> expensive operation as it traverses all the PTs (for some one who is
> just interested in getting that data for each vma).

Adding a new counter to a vma may cause a bouncing cacheline etc. I 
would think that such a counter is far more expensive than occasional 
scans through the page table because someone is curious about the 
number of page in use. /proc/<pid>/numa_maps also uses these scans to 
determine dirty pages etc.