mm: oom analysis: add shmem vmstat

Recently we encountered OOM problems due to memory use of the GEM cache.
Generally a large amuont of Shmem/Tmpfs pages tend to create a memory
shortage problem.

We often use the following calculation to determine the amount of shmem
pages:

shmem = NR_ACTIVE_ANON + NR_INACTIVE_ANON - NR_ANON_PAGES

however the expression does not consider isolated and mlocked pages.

This patch adds explicit accounting for pages used by shmem and tmpfs.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 13 insertions, 3 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index dd51c68e..bcc7372 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -119,6 +119,8 @@ void __remove_from_page_cache(struct page *page)
 	page->mapping = NULL;
 	mapping->nrpages--;
 	__dec_zone_page_state(page, NR_FILE_PAGES);
+	if (PageSwapBacked(page))
+		__dec_zone_page_state(page, NR_SHMEM);
 	BUG_ON(page_mapped(page));
 
 	/*
@@ -431,6 +433,8 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 		if (likely(!error)) {
 			mapping->nrpages++;
 			__inc_zone_page_state(page, NR_FILE_PAGES);
+			if (PageSwapBacked(page))
+				__inc_zone_page_state(page, NR_SHMEM);
 			spin_unlock_irq(&mapping->tree_lock);
 		} else {
 			page->mapping = NULL;
diff --git a/mm/migrate.c b/mm/migrate.c
index 0edeac9..37143b9 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -312,7 +312,10 @@ static int migrate_page_move_mapping(struct address_space *mapping,
 	 */
 	__dec_zone_page_state(page, NR_FILE_PAGES);
 	__inc_zone_page_state(newpage, NR_FILE_PAGES);
-
+	if (PageSwapBacked(page)) {
+		__dec_zone_page_state(page, NR_SHMEM);
+		__inc_zone_page_state(newpage, NR_SHMEM);
+	}
 	spin_unlock_irq(&mapping->tree_lock);
 
 	return 0;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4e050f3..e50c225 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2139,7 +2139,7 @@ void show_free_areas(void)
 		" unevictable:%lu"
 		" dirty:%lu writeback:%lu unstable:%lu buffer:%lu\n"
 		" free:%lu slab_reclaimable:%lu slab_unreclaimable:%lu\n"
-		" mapped:%lu pagetables:%lu bounce:%lu\n",
+		" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n",
 		global_page_state(NR_ACTIVE_ANON),
 		global_page_state(NR_ACTIVE_FILE),
 		global_page_state(NR_INACTIVE_ANON),
@@ -2153,6 +2153,7 @@ void show_free_areas(void)
 		global_page_state(NR_SLAB_RECLAIMABLE),
 		global_page_state(NR_SLAB_UNRECLAIMABLE),
 		global_page_state(NR_FILE_MAPPED),
+		global_page_state(NR_SHMEM),
 		global_page_state(NR_PAGETABLE),
 		global_page_state(NR_BOUNCE));
 
@@ -2175,6 +2176,7 @@ void show_free_areas(void)
 			" dirty:%lukB"
 			" writeback:%lukB"
 			" mapped:%lukB"
+			" shmem:%lukB"
 			" slab_reclaimable:%lukB"
 			" slab_unreclaimable:%lukB"
 			" kernel_stack:%lukB"
@@ -2200,6 +2202,7 @@ void show_free_areas(void)
 			K(zone_page_state(zone, NR_FILE_DIRTY)),
 			K(zone_page_state(zone, NR_WRITEBACK)),
 			K(zone_page_state(zone, NR_FILE_MAPPED)),
+			K(zone_page_state(zone, NR_SHMEM)),
 			K(zone_page_state(zone, NR_SLAB_RECLAIMABLE)),
 			K(zone_page_state(zone, NR_SLAB_UNRECLAIMABLE)),
 			zone_page_state(zone, NR_KERNEL_STACK) *
diff --git a/mm/vmstat.c b/mm/vmstat.c
index ceda39b..7214a45 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -644,7 +644,7 @@ static const char * const vmstat_text[] = {
 	"nr_bounce",
 	"nr_vmscan_write",
 	"nr_writeback_temp",
-
+	"nr_shmem",
 #ifdef CONFIG_NUMA
 	"numa_hit",
 	"numa_miss",