mm: introduce NR_UNRECLAIMABLE_PAGES

Introduce NR_UNRECLAIMABLE_PAGES memory counter which accounts
the pages that cannot be reclaimed under memory pressure.

Change-Id: I9afe50537b0d3c2e7ffc07916b23cce4329e3679
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>

include/linux/mmzone.h

@@ -184,6 +184,7 @@ enum node_stat_item {
 	NR_DIRTIED,		/* page dirtyings since bootup */
 	NR_WRITTEN,		/* page writings since bootup */
 	NR_INDIRECTLY_RECLAIMABLE_BYTES, /* measured in bytes */
+	NR_UNRECLAIMABLE_PAGES,
 	NR_VM_NODE_STAT_ITEMS
 };
 

mm/vmstat.c

@@ -1163,6 +1163,7 @@ const char * const vmstat_text[] = {
 	"nr_dirtied",
 	"nr_written",
 	"", /* nr_indirectly_reclaimable */
+	"nr_unreclaimable_pages",
 
 	/* enum writeback_stat_item counters */
 	"nr_dirty_threshold",