CHROMIUM: vmscan: add min_filelist_kbytes sysctl for protecting the working set

mm/vmscan.c

 /*
  *  linux/mm/vmscan.c
  *
  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  *
  *  Swap reorganised 29.12.95, Stephen Tweedie.
  *  kswapd added: 7.1.96  sct
  *  Removed kswapd_ctl limits, and swap out as many pages as needed
  *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
  *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
@@ skipping 112 matching lines @@
 #else
 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
 #endif
 
 /*
  * From 0 .. 100.  Higher means more swappy.
  */
 int vm_swappiness = 60;
 long vm_total_pages;    /* The total number of pages which the VM controls */
 
+/*
+ * Low watermark used to prevent fscache thrashing during low memory.
+ */
+int min_filelist_kbytes = 0;
+
 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
 #else
 #define scanning_global_lru(sc) (1)
 #endif
 
 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
@@ skipping 1360 matching lines @@
 
 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
                                 int file)
 {
         if (file)
                 return inactive_file_is_low(zone, sc);
         else
                 return inactive_anon_is_low(zone, sc);
 }
 
+/*
+ * Check low watermark used to prevent fscache thrashing during low memory.
+ */
+static int file_is_low(struct zone *zone, struct scan_control *sc)
+{
+        unsigned long pages_min, active, inactive;
+
+        if (!scanning_global_lru(sc))
+                return false;
+
+        pages_min = min_filelist_kbytes >> (PAGE_SHIFT - 10);
+        active = zone_page_state(zone, NR_ACTIVE_FILE);
+        inactive = zone_page_state(zone, NR_INACTIVE_FILE);
+
+        return ((active + inactive) < pages_min);
+}
+
 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
         struct zone *zone, struct scan_control *sc, int priority)
 {
         int file = is_file_lru(lru);
 
+        if (file && file_is_low(zone, sc))
+                return 0;
+
         if (is_active_lru(lru)) {
                 if (inactive_list_is_low(zone, sc, file))
                     shrink_active_list(nr_to_scan, zone, sc, priority, file);
                 return 0;
         }
 
         return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
 }
 
 /*
@@ skipping 1421 matching lines @@
 int scan_unevictable_register_node(struct node *node)
 {
         return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
 }
 
 void scan_unevictable_unregister_node(struct node *node)
 {
         sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
 }