vmscan: count the number of times zone_reclaim() scans and fails

[sfrench/cifs-2.6.git] / mm / vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f3a55d1f9ab7875386cc7df223ca5e538ca995b0..3018ad75613375c409f6a99d2e2a105604833c81 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1430,13 +1430,6 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
        unsigned long ap, fp;
        struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
 
-       /* If we have no swap space, do not bother scanning anon pages. */
-       if (!sc->may_swap || (nr_swap_pages <= 0)) {
-               percent[0] = 0;
-               percent[1] = 100;
-               return;
-       }
-
        anon  = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
                zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
        file  = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
@@ -1534,15 +1527,22 @@ static void shrink_zone(int priority, struct zone *zone,
        enum lru_list l;
        unsigned long nr_reclaimed = sc->nr_reclaimed;
        unsigned long swap_cluster_max = sc->swap_cluster_max;
+       int noswap = 0;
 
-       get_scan_ratio(zone, sc, percent);
+       /* If we have no swap space, do not bother scanning anon pages. */
+       if (!sc->may_swap || (nr_swap_pages <= 0)) {
+               noswap = 1;
+               percent[0] = 0;
+               percent[1] = 100;
+       } else
+               get_scan_ratio(zone, sc, percent);
 
        for_each_evictable_lru(l) {
                int file = is_file_lru(l);
                unsigned long scan;
 
                scan = zone_nr_pages(zone, sc, l);
-               if (priority) {
+               if (priority || noswap) {
                        scan >>= priority;
                        scan = (scan * percent[file]) / 100;
                }
@@ -2356,6 +2356,48 @@ int sysctl_min_unmapped_ratio = 1;
  */
 int sysctl_min_slab_ratio = 5;
 
+static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
+{
+       unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
+       unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
+               zone_page_state(zone, NR_ACTIVE_FILE);
+
+       /*
+        * It's possible for there to be more file mapped pages than
+        * accounted for by the pages on the file LRU lists because
+        * tmpfs pages accounted for as ANON can also be FILE_MAPPED
+        */
+       return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
+}
+
+/* Work out how many page cache pages we can reclaim in this reclaim_mode */
+static long zone_pagecache_reclaimable(struct zone *zone)
+{
+       long nr_pagecache_reclaimable;
+       long delta = 0;
+
+       /*
+        * If RECLAIM_SWAP is set, then all file pages are considered
+        * potentially reclaimable. Otherwise, we have to worry about
+        * pages like swapcache and zone_unmapped_file_pages() provides
+        * a better estimate
+        */
+       if (zone_reclaim_mode & RECLAIM_SWAP)
+               nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
+       else
+               nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
+
+       /* If we can't clean pages, remove dirty pages from consideration */
+       if (!(zone_reclaim_mode & RECLAIM_WRITE))
+               delta += zone_page_state(zone, NR_FILE_DIRTY);
+
+       /* Watch for any possible underflows due to delta */
+       if (unlikely(delta > nr_pagecache_reclaimable))
+               delta = nr_pagecache_reclaimable;
+
+       return nr_pagecache_reclaimable - delta;
+}
+
 /*
  * Try to free up some pages from this zone through reclaim.
  */
@@ -2390,9 +2432,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
        reclaim_state.reclaimed_slab = 0;
        p->reclaim_state = &reclaim_state;
 
-       if (zone_page_state(zone, NR_FILE_PAGES) -
-               zone_page_state(zone, NR_FILE_MAPPED) >
-               zone->min_unmapped_pages) {
+       if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
                /*
                 * Free memory by calling shrink zone with increasing
                 * priorities until we have enough memory freed.
@@ -2450,20 +2490,18 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
         * if less than a specified percentage of the zone is used by
         * unmapped file backed pages.
         */
-       if (zone_page_state(zone, NR_FILE_PAGES) -
-           zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
-           && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
-                       <= zone->min_slab_pages)
-               return 0;
+       if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
+           zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
+               return ZONE_RECLAIM_FULL;
 
        if (zone_is_all_unreclaimable(zone))
-               return 0;
+               return ZONE_RECLAIM_FULL;
 
        /*
         * Do not scan if the allocation should not be delayed.
         */
        if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
-                       return 0;
+               return ZONE_RECLAIM_NOSCAN;
 
        /*
         * Only run zone reclaim on the local zone or on zones that do not
@@ -2473,13 +2511,17 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
         */
        node_id = zone_to_nid(zone);
        if (node_state(node_id, N_CPU) && node_id != numa_node_id())
-               return 0;
+               return ZONE_RECLAIM_NOSCAN;
 
        if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
-               return 0;
+               return ZONE_RECLAIM_NOSCAN;
+
        ret = __zone_reclaim(zone, gfp_mask, order);
        zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
 
+       if (!ret)
+               count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
+
        return ret;
 }
 #endif