linux-kernel - [PATCH -mmotm-2009-12-10-17-19] Fix wrong rss count of smaps

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Date:	Mon, 28 Dec 2009 13:46:19 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	lkml <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Matt Mackall <mpm@...enic.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>
Subject: [PATCH -mmotm-2009-12-10-17-19] Fix wrong rss count of smaps

I am not sure we have to account zero page with file_rss. 
Hugh and Kame's new zero page doesn't do it. 
As side effect of this, we can prevent innocent process which have a lot
of zero page when OOM happens. 
(But I am not sure there is a process like this :)
So I think not file_rss counting is not bad. 

RSS counting zero page with file_rss helps any program using smaps?
If we have to keep the old behavior, I have to remake this patch. 

== CUT_HERE ==

Long time ago, We regards zero page as file_rss and
vm_normal_page doesn't return NULL.

But now, we reinstated ZERO_PAGE and vm_normal_page's implementation
can return NULL in case of zero page. Also we don't count it with
file_rss any more.

Then, RSS and PSS can't be matched.
For consistency, Let's ignore zero page in smaps_pte_range.

CC: Matt Mackall <mpm@...enic.com>
Signed-off-by: Minchan Kim <minchan.kim@...il.com>
---
 fs/proc/task_mmu.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 47c03f4..f277c4a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -361,12 +361,11 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 		if (!pte_present(ptent))
 			continue;

-		mss->resident += PAGE_SIZE;
-
 		page = vm_normal_page(vma, addr, ptent);
 		if (!page)
 			continue;

+		mss->resident += PAGE_SIZE;
 		/* Accumulate the size in pages that have been accessed. */
 		if (pte_young(ptent) || PageReferenced(page))
 			mss->referenced += PAGE_SIZE;
-- 
1.5.6.3

-- 
Kind regards,
Minchan Kim
--
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