[patch 2/3 take2] smaps: add pages referenced count to smaps

[David Rientjes <rientjes@google.com>]

Adds an additional unsigned long field to struct mem_size_stats:
referenced.  For each page table entry that is walked for the VMA in the
smaps code, this field is incremented by PAGE_SIZE if it has pte-reference
bits.

An additional line was added to the /proc/pid/smaps output for each VMA
to indicate how many pages within it are currently marked as accessed
(referenced).

Cc: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 fs/proc/task_mmu.c |   20 +++++++++++++-------
 1 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e87824b..50bd004 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -120,6 +120,7 @@ struct mem_size_stats
 	unsigned long shared_dirty;
 	unsigned long private_clean;
 	unsigned long private_dirty;
+	unsigned long referenced;
 };
 
 struct pte_walker {
@@ -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: %8lu kB\n",
 			   (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 >> 10);
 
 	if (m->count < m->size)  /* vma is copied successfully */
 		m->version = (vma != get_gate_vma(task))? vma->vm_start: 0;
@@ -302,6 +305,9 @@ static void smaps_pte_func(struct pte_walker *walker, pte_t *pte,
 	if (!page)
 		return;
 
+	/* Accumulate the number of pages that have been accessed. */
+	if (pte_young(ptent) || PageReferenced(page))
+		mss->referenced += PAGE_SIZE;
 	if (page_mapcount(page) >= 2) {
 		if (pte_dirty(ptent))
 			mss->shared_dirty += PAGE_SIZE;
-
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