include/linux/list_lru.h

   1 /*
   2  * Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
   3  * Authors: David Chinner and Glauber Costa
   4  *
   5  * Generic LRU infrastructure
   6  */
   7 #ifndef _LRU_LIST_H
   8 #define _LRU_LIST_H
   9
  10 #include <linux/list.h>
  11 #include <linux/nodemask.h>
  12 #include <linux/shrinker.h>
  13
  14 struct mem_cgroup;
  15
  16 /* list_lru_walk_cb has to always return one of those */
  17 enum lru_status {
  18         LRU_REMOVED,            /* item removed from list */
  19         LRU_REMOVED_RETRY,      /* item removed, but lock has been
  20                                    dropped and reacquired */
  21         LRU_ROTATE,             /* item referenced, give another pass */
  22         LRU_SKIP,               /* item cannot be locked, skip */
  23         LRU_RETRY,              /* item not freeable. May drop the lock
  24                                    internally, but has to return locked. */
  25 };
  26
  27 struct list_lru_one {
  28         struct list_head        list;
  29         /* may become negative during memcg reparenting */
  30         long                    nr_items;
  31 };
  32
  33 struct list_lru_memcg {
  34         /* array of per cgroup lists, indexed by memcg_cache_id */
  35         struct list_lru_one     *lru[0];
  36 };
  37
  38 struct list_lru_node {
  39         /* protects all lists on the node, including per cgroup */
  40         spinlock_t              lock;
  41         /* global list, used for the root cgroup in cgroup aware lrus */
  42         struct list_lru_one     lru;
  43 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
  44         /* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
  45         struct list_lru_memcg   *memcg_lrus;
  46 #endif
  47         long nr_items;
  48 } ____cacheline_aligned_in_smp;
  49
  50 struct list_lru {
  51         struct list_lru_node    *node;
  52 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
  53         struct list_head        list;
  54 #endif
  55 };
  56
  57 void list_lru_destroy(struct list_lru *lru);
  58 int __list_lru_init(struct list_lru *lru, bool memcg_aware,
  59                     struct lock_class_key *key);
  60
  61 #define list_lru_init(lru)              __list_lru_init((lru), false, NULL)
  62 #define list_lru_init_key(lru, key)     __list_lru_init((lru), false, (key))
  63 #define list_lru_init_memcg(lru)        __list_lru_init((lru), true, NULL)
  64
  65 int memcg_update_all_list_lrus(int num_memcgs);
  66 void memcg_drain_all_list_lrus(int src_idx, int dst_idx);
  67
  68 /**
  69  * list_lru_add: add an element to the lru list's tail
  70  * @list_lru: the lru pointer
  71  * @item: the item to be added.
  72  *
  73  * If the element is already part of a list, this function returns doing
  74  * nothing. Therefore the caller does not need to keep state about whether or
  75  * not the element already belongs in the list and is allowed to lazy update
  76  * it. Note however that this is valid for *a* list, not *this* list. If
  77  * the caller organize itself in a way that elements can be in more than
  78  * one type of list, it is up to the caller to fully remove the item from
  79  * the previous list (with list_lru_del() for instance) before moving it
  80  * to @list_lru
  81  *
  82  * Return value: true if the list was updated, false otherwise
  83  */
  84 bool list_lru_add(struct list_lru *lru, struct list_head *item);
  85
  86 /**
  87  * list_lru_del: delete an element to the lru list
  88  * @list_lru: the lru pointer
  89  * @item: the item to be deleted.
  90  *
  91  * This function works analogously as list_lru_add in terms of list
  92  * manipulation. The comments about an element already pertaining to
  93  * a list are also valid for list_lru_del.
  94  *
  95  * Return value: true if the list was updated, false otherwise
  96  */
  97 bool list_lru_del(struct list_lru *lru, struct list_head *item);
  98
  99 /**
 100  * list_lru_count_one: return the number of objects currently held by @lru
 101  * @lru: the lru pointer.
 102  * @nid: the node id to count from.
 103  * @memcg: the cgroup to count from.
 104  *
 105  * Always return a non-negative number, 0 for empty lists. There is no
 106  * guarantee that the list is not updated while the count is being computed.
 107  * Callers that want such a guarantee need to provide an outer lock.
 108  */
 109 unsigned long list_lru_count_one(struct list_lru *lru,
 110                                  int nid, struct mem_cgroup *memcg);
 111 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
 112
 113 static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
 114                                                   struct shrink_control *sc)
 115 {
 116         return list_lru_count_one(lru, sc->nid, sc->memcg);
 117 }
 118
 119 static inline unsigned long list_lru_count(struct list_lru *lru)
 120 {
 121         long count = 0;
 122         int nid;
 123
 124         for_each_node_state(nid, N_NORMAL_MEMORY)
 125                 count += list_lru_count_node(lru, nid);
 126
 127         return count;
 128 }
 129
 130 void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
 131 void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
 132                            struct list_head *head);
 133
 134 typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
 135                 struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
 136
 137 /**
 138  * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.
 139  * @lru: the lru pointer.
 140  * @nid: the node id to scan from.
 141  * @memcg: the cgroup to scan from.
 142  * @isolate: callback function that is resposible for deciding what to do with
 143  *  the item currently being scanned
 144  * @cb_arg: opaque type that will be passed to @isolate
 145  * @nr_to_walk: how many items to scan.
 146  *
 147  * This function will scan all elements in a particular list_lru, calling the
 148  * @isolate callback for each of those items, along with the current list
 149  * spinlock and a caller-provided opaque. The @isolate callback can choose to
 150  * drop the lock internally, but *must* return with the lock held. The callback
 151  * will return an enum lru_status telling the list_lru infrastructure what to
 152  * do with the object being scanned.
 153  *
 154  * Please note that nr_to_walk does not mean how many objects will be freed,
 155  * just how many objects will be scanned.
 156  *
 157  * Return value: the number of objects effectively removed from the LRU.
 158  */
 159 unsigned long list_lru_walk_one(struct list_lru *lru,
 160                                 int nid, struct mem_cgroup *memcg,
 161                                 list_lru_walk_cb isolate, void *cb_arg,
 162                                 unsigned long *nr_to_walk);
 163 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 164                                  list_lru_walk_cb isolate, void *cb_arg,
 165                                  unsigned long *nr_to_walk);
 166
 167 static inline unsigned long
 168 list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
 169                      list_lru_walk_cb isolate, void *cb_arg)
 170 {
 171         return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
 172                                  &sc->nr_to_scan);
 173 }
 174
 175 static inline unsigned long
 176 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
 177               void *cb_arg, unsigned long nr_to_walk)
 178 {
 179         long isolated = 0;
 180         int nid;
 181
 182         for_each_node_state(nid, N_NORMAL_MEMORY) {
 183                 isolated += list_lru_walk_node(lru, nid, isolate,
 184                                                cb_arg, &nr_to_walk);
 185                 if (nr_to_walk <= 0)
 186                         break;
 187         }
 188         return isolated;
 189 }
 190 #endif /* _LRU_LIST_H */