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 dd51c68e2b86..bcc7372aebbc 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 0edeac91348d..37143b924484 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 4e050f325ebd..e50c22545b8f 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 ceda39b63d7e..7214a4511257 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",