There are several FS shrinkers, including super_block::s_shrink, that
keep reclaimable objects in the list_lru structure. That said, to turn
them to memcg-aware shrinkers, it is enough to make list_lru per-memcg.
This patch does the trick. It adds an array of LRU lists to the list_lru
structure, one for each kmem-active memcg, and dispatches every item
addition or removal operation to the list corresponding to the memcg the
item is accounted to.
Since we already pass a shrink_control object to count and walk list_lru
functions to specify the NUMA node to scan, and the target memcg is held
in this structure, there is no need in changing the list_lru interface.
The idea lying behind the patch as well as the initial implementation
belong to Glauber Costa.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
include/linux/list_lru.h | 44 +++++++-
include/linux/memcontrol.h | 13 +++
mm/list_lru.c | 242 ++++++++++++++++++++++++++++++++++++++------
mm/memcontrol.c | 158 ++++++++++++++++++++++++++++-
4 files changed, 416 insertions(+), 41 deletions(-)
diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 34e57af..e8add3d 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -28,11 +28,47 @@ struct list_lru_node {
long nr_items;
} ____cacheline_aligned_in_smp;
+struct list_lru_one {
+ struct list_lru_node *node;
+ nodemask_t active_nodes;
+};
+
struct list_lru {
- struct list_lru_node *node;
- nodemask_t active_nodes;
+ struct list_lru_one global;
+#ifdef CONFIG_MEMCG_KMEM
+ /*
+ * In order to provide ability of scanning objects from different
+ * memory cgroups independently, we keep a separate LRU list for each
+ * kmem-active memcg in this array. The array is RCU-protected and
+ * indexed by memcg_cache_id().
+ */
+ struct list_lru_one **memcg;
+ /*
+ * Every time a kmem-active memcg is created or destroyed, we have to
+ * update the array of per-memcg LRUs in each list_lru structure. To
+ * achieve that, we keep all list_lru structures in the all_memcg_lrus
+ * list.
+ */
+ struct list_head list;
+ /*
+ * Since the array of per-memcg LRUs is RCU-protected, we can only free
+ * it after a call to synchronize_rcu(). To avoid multiple calls to
+ * synchronize_rcu() when a lot of LRUs get updated at the same time,
+ * which is a typical scenario, we will store the pointer to the
+ * previous version of the array in the memcg_old field for each
+ * list_lru structure, and then free them all at once after a single
+ * call to synchronize_rcu().
+ */
+ void *memcg_old;
+#endif /* CONFIG_MEMCG_KMEM */
};
+#ifdef CONFIG_MEMCG_KMEM
+int list_lru_memcg_alloc(struct list_lru *lru, int memcg_id);
+void list_lru_memcg_free(struct list_lru *lru, int memcg_id);
+int list_lru_grow_memcg(struct list_lru *lru, size_t new_array_size);
+#endif
+
void list_lru_destroy(struct list_lru *lru);
int list_lru_init(struct list_lru *lru);
@@ -70,7 +106,7 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item);
/**
* list_lru_count: return the number of objects currently held by @lru
* @lru: the lru pointer.
- * @sc: if not NULL, count only from node @sc->nid.
+ * @sc: if not NULL, count only from node @sc->nid and memcg @sc->memcg.
*
* Always return a non-negative number, 0 for empty lists. There is no
* guarantee that the list is not updated while the count is being computed.
@@ -83,7 +119,7 @@ typedef enum lru_status
/**
* list_lru_walk: walk a list_lru, isolating and disposing freeable items.
* @lru: the lru pointer.
- * @sc: if not NULL, scan only from node @sc->nid.
+ * @sc: if not NULL, scan only from node @sc->nid and memcg @sc->memcg.
* @isolate: callback function that is resposible for deciding what to do with
* the item currently being scanned
* @cb_arg: opaque type that will be passed to @isolate
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index c0f24a9..4c88d72 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -29,6 +29,7 @@ struct page_cgroup;
struct page;
struct mm_struct;
struct kmem_cache;
+struct list_lru;
/*
* The corresponding mem_cgroup_stat_names is defined in mm/memcontrol.c,
@@ -523,6 +524,9 @@ __memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp);
void mem_cgroup_destroy_cache(struct kmem_cache *cachep);
void kmem_cache_destroy_memcg_children(struct kmem_cache *s);
+int memcg_list_lru_init(struct list_lru *lru);
+void memcg_list_lru_destroy(struct list_lru *lru);
+
/**
* memcg_kmem_newpage_charge: verify if a new kmem allocation is allowed.
* @gfp: the gfp allocation flags.
@@ -687,6 +691,15 @@ memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
static inline void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
{
}
+
+static inline int memcg_list_lru_init(struct list_lru *lru)
+{
+ return 0;
+}
+
+static inline void memcg_list_lru_destroy(struct list_lru *lru)
+{
+}
#endif /* CONFIG_MEMCG_KMEM */
#endif /* _LINUX_MEMCONTROL_H */
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 7d4a9c2..1c0f39a 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -9,19 +9,70 @@
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/shrinker.h>
+#include <linux/memcontrol.h>
+#include <linux/page_cgroup.h>
#include <linux/list_lru.h>
+#ifdef CONFIG_MEMCG_KMEM
+static struct list_lru_one *lru_of_index(struct list_lru *lru,
+ int memcg_id)
+{
+ struct list_lru_one **memcg_lrus;
+ struct list_lru_one *olru;
+
+ if (memcg_id < 0)
+ return &lru->global;
+
+ rcu_read_lock();
+ memcg_lrus = rcu_dereference(lru->memcg);
+ olru = memcg_lrus[memcg_id];
+ rcu_read_unlock();
+
+ return olru;
+}
+
+static struct list_lru_one *lru_of_page(struct list_lru *lru,
+ struct page *page)
+{
+ struct mem_cgroup *memcg = NULL;
+ struct page_cgroup *pc;
+
+ pc = lookup_page_cgroup(compound_head(page));
+ if (PageCgroupUsed(pc)) {
+ lock_page_cgroup(pc);
+ if (PageCgroupUsed(pc))
+ memcg = pc->mem_cgroup;
+ unlock_page_cgroup(pc);
+ }
+ return lru_of_index(lru, memcg_cache_id(memcg));
+}
+#else
+static inline struct list_lru_one *lru_of_index(struct list_lru *lru,
+ int memcg_id)
+{
+ return &lru->global;
+}
+
+static inline struct list_lru_one *lru_of_page(struct list_lru *lru,
+ struct page *page)
+{
+ return &lru->global;
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
bool list_lru_add(struct list_lru *lru, struct list_head *item)
{
- int nid = page_to_nid(virt_to_page(item));
- struct list_lru_node *nlru = &lru->node[nid];
+ struct page *page = virt_to_page(item);
+ int nid = page_to_nid(page);
+ struct list_lru_one *olru = lru_of_page(lru, page);
+ struct list_lru_node *nlru = &olru->node[nid];
spin_lock(&nlru->lock);
WARN_ON_ONCE(nlru->nr_items < 0);
if (list_empty(item)) {
list_add_tail(item, &nlru->list);
if (nlru->nr_items++ == 0)
- node_set(nid, lru->active_nodes);
+ node_set(nid, olru->active_nodes);
spin_unlock(&nlru->lock);
return true;
}
@@ -32,14 +83,16 @@ EXPORT_SYMBOL_GPL(list_lru_add);
bool list_lru_del(struct list_lru *lru, struct list_head *item)
{
- int nid = page_to_nid(virt_to_page(item));
- struct list_lru_node *nlru = &lru->node[nid];
+ struct page *page = virt_to_page(item);
+ int nid = page_to_nid(page);
+ struct list_lru_one *olru = lru_of_page(lru, page);
+ struct list_lru_node *nlru = &olru->node[nid];
spin_lock(&nlru->lock);
if (!list_empty(item)) {
list_del_init(item);
if (--nlru->nr_items == 0)
- node_clear(nid, lru->active_nodes);
+ node_clear(nid, olru->active_nodes);
WARN_ON_ONCE(nlru->nr_items < 0);
spin_unlock(&nlru->lock);
return true;
@@ -50,10 +103,10 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item)
EXPORT_SYMBOL_GPL(list_lru_del);
static unsigned long
-list_lru_count_node(struct list_lru *lru, int nid)
+list_lru_count_node(struct list_lru_one *olru, int nid)
{
unsigned long count = 0;
- struct list_lru_node *nlru = &lru->node[nid];
+ struct list_lru_node *nlru = &olru->node[nid];
spin_lock(&nlru->lock);
WARN_ON_ONCE(nlru->nr_items < 0);
@@ -67,23 +120,36 @@ unsigned long list_lru_count(struct list_lru *lru, struct shrink_control *sc)
{
long count = 0;
int nid;
+ struct list_lru_one *olru;
+ struct mem_cgroup *memcg;
- if (sc)
- return list_lru_count_node(lru, sc->nid);
+ if (sc) {
+ olru = lru_of_index(lru, memcg_cache_id(sc->memcg));
+ return list_lru_count_node(olru, sc->nid);
+ }
+
+ memcg = NULL;
+ do {
+ if (memcg && !memcg_kmem_is_active(memcg))
+ goto next;
- for_each_node_mask(nid, lru->active_nodes)
- count += list_lru_count_node(lru, nid);
+ olru = lru_of_index(lru, memcg_cache_id(memcg));
+ for_each_node_mask(nid, olru->active_nodes)
+ count += list_lru_count_node(olru, nid);
+next:
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ } while (memcg);
return count;
}
EXPORT_SYMBOL_GPL(list_lru_count);
static unsigned long
-list_lru_walk_node(struct list_lru *lru, int nid, list_lru_walk_cb isolate,
+list_lru_walk_node(struct list_lru_one *olru, int nid, list_lru_walk_cb isolate,
void *cb_arg, unsigned long *nr_to_walk)
{
- struct list_lru_node *nlru = &lru->node[nid];
+ struct list_lru_node *nlru = &olru->node[nid];
struct list_head *item, *n;
unsigned long isolated = 0;
@@ -104,7 +170,7 @@ restart:
switch (ret) {
case LRU_REMOVED:
if (--nlru->nr_items == 0)
- node_clear(nid, lru->active_nodes);
+ node_clear(nid, olru->active_nodes);
WARN_ON_ONCE(nlru->nr_items < 0);
isolated++;
break;
@@ -134,42 +200,154 @@ unsigned long list_lru_walk(struct list_lru *lru, struct shrink_control *sc,
{
long isolated = 0;
int nid;
+ struct list_lru_one *olru;
+ struct mem_cgroup *memcg;
- if (sc)
- return list_lru_walk_node(lru, sc->nid, isolate,
+ if (sc) {
+ olru = lru_of_index(lru, memcg_cache_id(sc->memcg));
+ return list_lru_walk_node(olru, sc->nid, isolate,
cb_arg, nr_to_walk);
-
- for_each_node_mask(nid, lru->active_nodes) {
- isolated += list_lru_walk_node(lru, nid, isolate,
- cb_arg, nr_to_walk);
- if (*nr_to_walk <= 0)
- break;
}
+
+ memcg = NULL;
+ do {
+ if (memcg && !memcg_kmem_is_active(memcg))
+ goto next;
+
+ olru = lru_of_index(lru, memcg_cache_id(memcg));
+ for_each_node_mask(nid, olru->active_nodes) {
+ isolated += list_lru_walk_node(olru, nid, isolate,
+ cb_arg, nr_to_walk);
+ if (*nr_to_walk <= 0) {
+ mem_cgroup_iter_break(NULL, memcg);
+ goto out;
+ }
+ }
+next:
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ } while (memcg);
+out:
return isolated;
}
EXPORT_SYMBOL_GPL(list_lru_walk);
-int list_lru_init(struct list_lru *lru)
+static int list_lru_init_one(struct list_lru_one *olru)
{
int i;
- size_t size = sizeof(*lru->node) * nr_node_ids;
- lru->node = kzalloc(size, GFP_KERNEL);
- if (!lru->node)
+ olru->node = kcalloc(nr_node_ids, sizeof(*olru->node), GFP_KERNEL);
+ if (!olru->node)
return -ENOMEM;
- nodes_clear(lru->active_nodes);
+ nodes_clear(olru->active_nodes);
for (i = 0; i < nr_node_ids; i++) {
- spin_lock_init(&lru->node[i].lock);
- INIT_LIST_HEAD(&lru->node[i].list);
- lru->node[i].nr_items = 0;
+ struct list_lru_node *nlru = &olru->node[i];
+
+ spin_lock_init(&nlru->lock);
+ INIT_LIST_HEAD(&nlru->list);
+ nlru->nr_items = 0;
}
return 0;
}
+
+static void list_lru_destroy_one(struct list_lru_one *olru)
+{
+ kfree(olru->node);
+}
+
+int list_lru_init(struct list_lru *lru)
+{
+ int err;
+
+ err = list_lru_init_one(&lru->global);
+ if (err)
+ goto fail;
+
+ err = memcg_list_lru_init(lru);
+ if (err)
+ goto fail;
+
+ return 0;
+fail:
+ list_lru_destroy_one(&lru->global);
+ lru->global.node = NULL; /* see list_lru_destroy() */
+ return err;
+}
EXPORT_SYMBOL_GPL(list_lru_init);
void list_lru_destroy(struct list_lru *lru)
{
- kfree(lru->node);
+ /*
+ * It is common throughout the kernel source tree to call the
+ * destructor on a zeroed out object that has not been initialized or
+ * whose initialization failed, because it greatly simplifies fail
+ * paths. Once the list_lru structure was implemented, its destructor
+ * consisted of the only call to kfree() and thus conformed to the
+ * rule, but as it growed, it became more complex so that calling
+ * destructor on an uninitialized object would be a bug. To preserve
+ * backward compatibility, we explicitly exit the destructor if the
+ * object seems to be uninitialized.
+ */
+ if (!lru->global.node)
+ return;
+
+ list_lru_destroy_one(&lru->global);
+ memcg_list_lru_destroy(lru);
}
EXPORT_SYMBOL_GPL(list_lru_destroy);
+
+#ifdef CONFIG_MEMCG_KMEM
+int list_lru_memcg_alloc(struct list_lru *lru, int memcg_id)
+{
+ int err;
+ struct list_lru_one *olru;
+
+ olru = kmalloc(sizeof(*olru), GFP_KERNEL);
+ if (!olru)
+ return -ENOMEM;
+
+ err = list_lru_init_one(olru);
+ if (err) {
+ kfree(olru);
+ return err;
+ }
+
+ VM_BUG_ON(lru->memcg[memcg_id]);
+ lru->memcg[memcg_id] = olru;
+ return 0;
+}
+
+void list_lru_memcg_free(struct list_lru *lru, int memcg_id)
+{
+ struct list_lru_one *olru;
+
+ olru = lru->memcg[memcg_id];
+ if (olru) {
+ list_lru_destroy_one(olru);
+ kfree(olru);
+ lru->memcg[memcg_id] = NULL;
+ }
+}
+
+int list_lru_grow_memcg(struct list_lru *lru, size_t new_array_size)
+{
+ int i;
+ struct list_lru_one **memcg_lrus;
+
+ memcg_lrus = kcalloc(new_array_size, sizeof(*memcg_lrus), GFP_KERNEL);
+ if (!memcg_lrus)
+ return -ENOMEM;
+
+ if (lru->memcg) {
+ for_each_memcg_cache_index(i) {
+ if (lru->memcg[i])
+ memcg_lrus[i] = lru->memcg[i];
+ }
+ }
+
+ VM_BUG_ON(lru->memcg_old);
+ lru->memcg_old = lru->memcg;
+ rcu_assign_pointer(lru->memcg, memcg_lrus);
+ return 0;
+}
+#endif /* CONFIG_MEMCG_KMEM */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a3f479b..b15219e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -55,6 +55,7 @@
#include <linux/cpu.h>
#include <linux/oom.h>
#include <linux/lockdep.h>
+#include <linux/list_lru.h>
#include "internal.h"
#include <net/sock.h>
#include <net/ip.h>
@@ -3034,6 +3035,137 @@ static size_t memcg_caches_array_size(int num_groups)
}
/*
+ * The list of all list_lru structures. Protected by memcg_create_mutex.
+ * Needed for updating all per-memcg LRUs whenever a kmem-enabled memcg is
+ * created or destroyed.
+ */
+static LIST_HEAD(all_memcg_lrus);
+
+static void __memcg_destroy_all_lrus(int memcg_id)
+{
+ struct list_lru *lru;
+
+ list_for_each_entry(lru, &all_memcg_lrus, list)
+ list_lru_memcg_free(lru, memcg_id);
+}
+
+/*
+ * This function is called when a kmem-active memcg is destroyed in order to
+ * free LRUs corresponding to the memcg in all list_lru structures.
+ */
+static void memcg_destroy_all_lrus(struct mem_cgroup *memcg)
+{
+ int memcg_id;
+
+ memcg_id = memcg_cache_id(memcg);
+ if (memcg_id >= 0) {
+ mutex_lock(&memcg_create_mutex);
+ __memcg_destroy_all_lrus(memcg_id);
+ mutex_unlock(&memcg_create_mutex);
+ }
+}
+
+/*
+ * This function allocates LRUs for a memcg in all list_lru structures. It is
+ * called under memcg_create_mutex when a new kmem-active memcg is added.
+ */
+static int memcg_init_all_lrus(int new_memcg_id)
+{
+ int err = 0;
+ int num_memcgs = new_memcg_id + 1;
+ int grow = (num_memcgs > memcg_limited_groups_array_size);
+ size_t new_array_size = memcg_caches_array_size(num_memcgs);
+ struct list_lru *lru;
+
+ if (grow) {
+ list_for_each_entry(lru, &all_memcg_lrus, list) {
+ err = list_lru_grow_memcg(lru, new_array_size);
+ if (err)
+ goto out;
+ }
+ }
+
+ list_for_each_entry(lru, &all_memcg_lrus, list) {
+ err = list_lru_memcg_alloc(lru, new_memcg_id);
+ if (err) {
+ __memcg_destroy_all_lrus(new_memcg_id);
+ break;
+ }
+ }
+out:
+ if (grow) {
+ synchronize_rcu();
+ list_for_each_entry(lru, &all_memcg_lrus, list) {
+ kfree(lru->memcg_old);
+ lru->memcg_old = NULL;
+ }
+ }
+ return err;
+}
+
+int memcg_list_lru_init(struct list_lru *lru)
+{
+ int err = 0;
+ int i;
+ struct mem_cgroup *memcg;
+
+ lru->memcg = NULL;
+ lru->memcg_old = NULL;
+
+ mutex_lock(&memcg_create_mutex);
+ if (!memcg_kmem_enabled())
+ goto out_list_add;
+
+ lru->memcg = kcalloc(memcg_limited_groups_array_size,
+ sizeof(*lru->memcg), GFP_KERNEL);
+ if (!lru->memcg) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ for_each_mem_cgroup(memcg) {
+ int memcg_id;
+
+ memcg_id = memcg_cache_id(memcg);
+ if (memcg_id < 0)
+ continue;
+
+ err = list_lru_memcg_alloc(lru, memcg_id);
+ if (err) {
+ mem_cgroup_iter_break(NULL, memcg);
+ goto out_free_lru_memcg;
+ }
+ }
+out_list_add:
+ list_add(&lru->list, &all_memcg_lrus);
+out:
+ mutex_unlock(&memcg_create_mutex);
+ return err;
+
+out_free_lru_memcg:
+ for (i = 0; i < memcg_limited_groups_array_size; i++)
+ list_lru_memcg_free(lru, i);
+ kfree(lru->memcg);
+ goto out;
+}
+
+void memcg_list_lru_destroy(struct list_lru *lru)
+{
+ int i, array_size;
+
+ mutex_lock(&memcg_create_mutex);
+ list_del(&lru->list);
+ array_size = memcg_limited_groups_array_size;
+ mutex_unlock(&memcg_create_mutex);
+
+ if (lru->memcg) {
+ for (i = 0; i < array_size; i++)
+ list_lru_memcg_free(lru, i);
+ kfree(lru->memcg);
+ }
+}
+
+/*
* This is a bit cumbersome, but it is rarely used and avoids a backpointer
* in the memcg_cache_params struct.
*/
@@ -3164,15 +3296,30 @@ int memcg_update_cache_sizes(struct mem_cgroup *memcg)
*/
memcg_kmem_set_activated(memcg);
+ /*
+ * We need to init the memcg lru lists before we update the caches.
+ * Once the caches are updated, they will be able to start hosting
+ * objects. If a cache is created very quickly and an element is used
+ * and disposed to the lru quickly as well, we can end up with a NULL
+ * pointer dereference while trying to add a new element to a memcg
+ * lru.
+ */
+ ret = memcg_init_all_lrus(num);
+ if (ret)
+ goto out;
+
ret = memcg_update_all_caches(num+1);
- if (ret) {
- ida_simple_remove(&kmem_limited_groups, num);
- memcg_kmem_clear_activated(memcg);
- return ret;
- }
+ if (ret)
+ goto out_destroy_all_lrus;
memcg->kmemcg_id = num;
return 0;
+out_destroy_all_lrus:
+ __memcg_destroy_all_lrus(num);
+out:
+ ida_simple_remove(&kmem_limited_groups, num);
+ memcg_kmem_clear_activated(memcg);
+ return ret;
}
/*
@@ -5955,6 +6102,7 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
static void memcg_destroy_kmem(struct mem_cgroup *memcg)
{
mem_cgroup_sockets_destroy(memcg);
+ memcg_destroy_all_lrus(memcg);
}
static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
--
1.7.10.4
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