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 } ____cacheline_aligned_in_smp;
  48
  49 struct list_lru {
  50         struct list_lru_node    *node;
  51 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
  52         struct list_head        list;
  53 #endif
  54 };
  55
  56 void list_lru_destroy(struct list_lru *lru);
  57 int __list_lru_init(struct list_lru *lru, bool memcg_aware,
  58                     struct lock_class_key *key);
  59
  60 #define list_lru_init(lru)              __list_lru_init((lru), false, NULL)
  61 #define list_lru_init_key(lru, key)     __list_lru_init((lru), false, (key))
  62 #define list_lru_init_memcg(lru)        __list_lru_init((lru), true, NULL)
  63
  64 int memcg_update_all_list_lrus(int num_memcgs);
  65 void memcg_drain_all_list_lrus(int src_idx, int dst_idx);
  66
  67 /**
  68  * list_lru_add: add an element to the lru list's tail
  69  * @list_lru: the lru pointer
  70  * @item: the item to be added.
  71  *
  72  * If the element is already part of a list, this function returns doing
  73  * nothing. Therefore the caller does not need to keep state about whether or
  74  * not the element already belongs in the list and is allowed to lazy update
  75  * it. Note however that this is valid for *a* list, not *this* list. If
  76  * the caller organize itself in a way that elements can be in more than
  77  * one type of list, it is up to the caller to fully remove the item from
  78  * the previous list (with list_lru_del() for instance) before moving it
  79  * to @list_lru
  80  *
  81  * Return value: true if the list was updated, false otherwise
  82  */
  83 bool list_lru_add(struct list_lru *lru, struct list_head *item);
  84
  85 /**
  86  * list_lru_del: delete an element to the lru list
  87  * @list_lru: the lru pointer
  88  * @item: the item to be deleted.
  89  *
  90  * This function works analogously as list_lru_add in terms of list
  91  * manipulation. The comments about an element already pertaining to
  92  * a list are also valid for list_lru_del.
  93  *
  94  * Return value: true if the list was updated, false otherwise
  95  */
  96 bool list_lru_del(struct list_lru *lru, struct list_head *item);
  97
  98 /**
  99  * list_lru_count_one: return the number of objects currently held by @lru
 100  * @lru: the lru pointer.
 101  * @nid: the node id to count from.
 102  * @memcg: the cgroup to count from.
 103  *
 104  * Always return a non-negative number, 0 for empty lists. There is no
 105  * guarantee that the list is not updated while the count is being computed.
 106  * Callers that want such a guarantee need to provide an outer lock.
 107  */
 108 unsigned long list_lru_count_one(struct list_lru *lru,
 109                                  int nid, struct mem_cgroup *memcg);
 110 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
 111
 112 static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
 113                                                   struct shrink_control *sc)
 114 {
 115         return list_lru_count_one(lru, sc->nid, sc->memcg);
 116 }
 117
 118 static inline unsigned long list_lru_count(struct list_lru *lru)
 119 {
 120         long count = 0;
 121         int nid;
 122
 123         for_each_node_state(nid, N_NORMAL_MEMORY)
 124                 count += list_lru_count_node(lru, nid);
 125
 126         return count;
 127 }
 128
 129 void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
 130 void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
 131                            struct list_head *head);
 132
 133 typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
 134                 struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
 135
 136 /**
 137  * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.
 138  * @lru: the lru pointer.
 139  * @nid: the node id to scan from.
 140  * @memcg: the cgroup to scan from.
 141  * @isolate: callback function that is resposible for deciding what to do with
 142  *  the item currently being scanned
 143  * @cb_arg: opaque type that will be passed to @isolate
 144  * @nr_to_walk: how many items to scan.
 145  *
 146  * This function will scan all elements in a particular list_lru, calling the
 147  * @isolate callback for each of those items, along with the current list
 148  * spinlock and a caller-provided opaque. The @isolate callback can choose to
 149  * drop the lock internally, but *must* return with the lock held. The callback
 150  * will return an enum lru_status telling the list_lru infrastructure what to
 151  * do with the object being scanned.
 152  *
 153  * Please note that nr_to_walk does not mean how many objects will be freed,
 154  * just how many objects will be scanned.
 155  *
 156  * Return value: the number of objects effectively removed from the LRU.
 157  */
 158 unsigned long list_lru_walk_one(struct list_lru *lru,
 159                                 int nid, struct mem_cgroup *memcg,
 160                                 list_lru_walk_cb isolate, void *cb_arg,
 161                                 unsigned long *nr_to_walk);
 162 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 163                                  list_lru_walk_cb isolate, void *cb_arg,
 164                                  unsigned long *nr_to_walk);
 165
 166 static inline unsigned long
 167 list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
 168                      list_lru_walk_cb isolate, void *cb_arg)
 169 {
 170         return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
 171                                  &sc->nr_to_scan);
 172 }
 173
 174 static inline unsigned long
 175 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
 176               void *cb_arg, unsigned long nr_to_walk)
 177 {
 178         long isolated = 0;
 179         int nid;
 180
 181         for_each_node_state(nid, N_NORMAL_MEMORY) {
 182                 isolated += list_lru_walk_node(lru, nid, isolate,
 183                                                cb_arg, &nr_to_walk);
 184                 if (nr_to_walk <= 0)
 185                         break;
 186         }
 187         return isolated;
 188 }
 189 #endif /* _LRU_LIST_H */