FS-shrinkers, which shrink dcaches and icaches, keep dentries and inodes
in list_lru structures in order to evict least recently used objects.
With per-memcg kmem shrinking infrastructure introduced, we have to make
those LRU lists per-memcg in order to allow shrinking FS caches that
belong to different memory cgroups independently.
This patch addresses the issue by introducing struct memcg_list_lru.
This struct aggregates list_lru objects for each kmem-active memcg, and
keeps it uptodate whenever a memcg is created or destroyed. Its
interface is very simple: it only allows to get the pointer to the
appropriate list_lru object from a memcg or a kmem ptr, which should be
further operated with conventional list_lru methods.
Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
Cc: Glauber Costa <glom...@openvz.org>
Cc: Dave Chinner <dchin...@redhat.com>
Cc: Mel Gorman <mgor...@suse.de>
Cc: Rik van Riel <r...@redhat.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Michal Hocko <mho...@suse.cz>
Cc: Hugh Dickins <hu...@google.com>
Cc: Kamezawa Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
Cc: Andrew Morton <a...@linux-foundation.org>
---
include/linux/list_lru.h | 56 ++++++++++
mm/memcontrol.c | 256 ++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 306 insertions(+), 6 deletions(-)
diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 3ce5417..b3b3b86 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -10,6 +10,8 @@
#include <linux/list.h>
#include <linux/nodemask.h>
+struct mem_cgroup;
+
/* list_lru_walk_cb has to always return one of those */
enum lru_status {
LRU_REMOVED, /* item removed from list */
@@ -31,6 +33,27 @@ struct list_lru {
nodemask_t active_nodes;
};
+struct memcg_list_lru {
+ struct list_lru global_lru;
+
+#ifdef CONFIG_MEMCG_KMEM
+ struct list_lru **memcg_lrus; /* rcu-protected array of per-memcg
+ lrus, indexed by memcg_cache_id() */
+
+ struct list_head list; /* list of all memcg-aware lrus */
+
+ /*
+ * The memcg_lrus array is rcu protected, so we can only free it after
+ * a call to synchronize_rcu(). To avoid multiple calls to
+ * synchronize_rcu() when many 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 old_lrus variable for each lru, and then
+ * free them all at once after a single call to synchronize_rcu().
+ */
+ void *old_lrus;
+#endif
+};
+
void list_lru_destroy(struct list_lru *lru);
int list_lru_init(struct list_lru *lru);
@@ -128,4 +151,37 @@ list_lru_walk(struct list_lru *lru, list_lru_walk_cb
isolate,
}
return isolated;
}
+
+#ifdef CONFIG_MEMCG_KMEM
+int memcg_list_lru_init(struct memcg_list_lru *lru);
+void memcg_list_lru_destroy(struct memcg_list_lru *lru);
+
+struct list_lru *
+mem_cgroup_list_lru(struct memcg_list_lru *lru, struct mem_cgroup *memcg);
+struct list_lru *
+mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr);
+#else
+static inline int memcg_list_lru_init(struct memcg_list_lru *lru)
+{
+ return list_lru_init(&lru->global_lru);
+}
+
+static inline void memcg_list_lru_destroy(struct memcg_list_lru *lru)
+{
+ list_lru_destroy(&lru->global_lru);
+}
+
+static inline struct list_lru *
+mem_cgroup_list_lru(struct memcg_list_lru *lru, struct mem_cgroup *memcg)
+{
+ return &lru->global_lru;
+}
+
+static inline struct list_lru *
+mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr)
+{
+ return &lru->global_lru;
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
#endif /* _LRU_LIST_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f5d7128..84f1ca3 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>
@@ -3249,6 +3250,8 @@ void memcg_cache_list_add(struct mem_cgroup *memcg,
struct kmem_cache *cachep)
mutex_unlock(&memcg->slab_caches_mutex);
}
+static int memcg_update_all_lrus(int num_groups);
+
/*
* This ends up being protected by the set_limit mutex, during normal
* operation, because that is its main call site.
@@ -3273,15 +3276,28 @@ int memcg_update_cache_sizes(struct mem_cgroup *memcg)
*/
memcg_kmem_set_activated(memcg);
- ret = memcg_update_all_caches(num+1);
- if (ret) {
- ida_simple_remove(&kmem_limited_groups, num);
- memcg_kmem_clear_activated(memcg);
- return ret;
- }
+ /*
+ * We need to update 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_update_all_lrus(num + 1);
+ if (ret)
+ goto out;
+
+ ret = memcg_update_all_caches(num + 1);
+ if (ret)
+ goto out;
memcg->kmemcg_id = num;
return 0;
+out:
+ ida_simple_remove(&kmem_limited_groups, num);
+ memcg_kmem_clear_activated(memcg);
+ return ret;
}
static size_t memcg_caches_array_size(int num_groups)
@@ -3881,6 +3897,233 @@ void __memcg_kmem_uncharge_pages(struct page *page, int
order)
VM_BUG_ON(mem_cgroup_is_root(memcg));
memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
}
+
+static LIST_HEAD(memcg_lrus_list);
+
+static int alloc_memcg_lru(struct memcg_list_lru *lru, int memcg_id)
+{
+ int err;
+ struct list_lru *memcg_lru;
+
+ memcg_lru = kmalloc(sizeof(*memcg_lru), GFP_KERNEL);
+ if (!memcg_lru)
+ return -ENOMEM;
+
+ err = list_lru_init(memcg_lru);
+ if (err) {
+ kfree(memcg_lru);
+ return err;
+ }
+
+ VM_BUG_ON(lru->memcg_lrus[memcg_id]);
+ lru->memcg_lrus[memcg_id] = memcg_lru;
+ return 0;
+}
+
+static void free_memcg_lru(struct memcg_list_lru *lru, int memcg_id)
+{
+ struct list_lru *memcg_lru = NULL;
+
+ swap(lru->memcg_lrus[memcg_id], memcg_lru);
+ if (memcg_lru) {
+ list_lru_destroy(memcg_lru);
+ kfree(memcg_lru);
+ }
+}
+
+static int memcg_list_lru_grow(struct memcg_list_lru *lru, int num_groups)
+{
+ struct list_lru **new_lrus;
+
+ new_lrus = kcalloc(memcg_caches_array_size(num_groups),
+ sizeof(*new_lrus), GFP_KERNEL);
+ if (!new_lrus)
+ return -ENOMEM;
+
+ if (lru->memcg_lrus) {
+ int i;
+
+ for_each_memcg_cache_index(i) {
+ if (lru->memcg_lrus[i])
+ new_lrus[i] = lru->memcg_lrus[i];
+ }
+ }
+
+ lru->old_lrus = lru->memcg_lrus;
+ rcu_assign_pointer(lru->memcg_lrus, new_lrus);
+ return 0;
+}
+
+static void __memcg_destroy_all_lrus(int memcg_id)
+{
+ struct memcg_list_lru *lru;
+
+ list_for_each_entry(lru, &memcg_lrus_list, list)
+ free_memcg_lru(lru, memcg_id);
+}
+
+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);
+ }
+}
+
+static int memcg_update_all_lrus(int num_groups)
+{
+ int err = 0;
+ struct memcg_list_lru *lru;
+ int new_memcg_id = num_groups - 1;
+ int grow = (num_groups > memcg_limited_groups_array_size);
+
+ memcg_stop_kmem_account();
+ if (grow) {
+ list_for_each_entry(lru, &memcg_lrus_list, list) {
+ err = memcg_list_lru_grow(lru, num_groups);
+ if (err)
+ goto free_old_lrus;
+ }
+ }
+ list_for_each_entry(lru, &memcg_lrus_list, list) {
+ err = alloc_memcg_lru(lru, new_memcg_id);
+ if (err) {
+ __memcg_destroy_all_lrus(new_memcg_id);
+ break;
+ }
+ }
+free_old_lrus:
+ if (grow) {
+ /* free previous versions of memcg_lrus arrays */
+ synchronize_rcu();
+ list_for_each_entry(lru, &memcg_lrus_list, list) {
+ kfree(lru->old_lrus);
+ lru->old_lrus = NULL;
+ }
+ }
+ memcg_resume_kmem_account();
+ return err;
+}
+
+static void __memcg_list_lru_destroy(struct memcg_list_lru *lru)
+{
+ int i;
+
+ if (lru->memcg_lrus) {
+ for_each_memcg_cache_index(i)
+ free_memcg_lru(lru, i);
+ }
+}
+
+static int __memcg_list_lru_init(struct memcg_list_lru *lru)
+{
+ int err = 0;
+ struct mem_cgroup *memcg;
+
+ if (!memcg_kmem_enabled())
+ return 0;
+
+ memcg_stop_kmem_account();
+ lru->memcg_lrus = kcalloc(memcg_limited_groups_array_size,
+ sizeof(*lru->memcg_lrus), GFP_KERNEL);
+ if (!lru->memcg_lrus)
+ return -ENOMEM;
+
+ for_each_mem_cgroup(memcg) {
+ int memcg_id;
+
+ memcg_id = memcg_cache_id(memcg);
+ if (memcg_id < 0)
+ continue;
+
+ err = alloc_memcg_lru(lru, memcg_id);
+ if (err) {
+ mem_cgroup_iter_break(root_mem_cgroup, memcg);
+ goto out;
+ }
+ }
+out:
+ if (err)
+ __memcg_list_lru_destroy(lru);
+ memcg_resume_kmem_account();
+ return err;
+}
+
+int memcg_list_lru_init(struct memcg_list_lru *lru)
+{
+ int err;
+
+ memset(lru, 0, sizeof(*lru));
+
+ err = list_lru_init(&lru->global_lru);
+ if (err)
+ return err;
+
+ mutex_lock(&memcg_create_mutex);
+ err = __memcg_list_lru_init(lru);
+ if (!err)
+ list_add(&lru->list, &memcg_lrus_list);
+ mutex_unlock(&memcg_create_mutex);
+
+ if (err)
+ list_lru_destroy(&lru->global_lru);
+ return err;
+}
+
+void memcg_list_lru_destroy(struct memcg_list_lru *lru)
+{
+ /* either the lru was not initialized or initialization failed,
+ * in either way we have nothing to do */
+ if (!lru->list.next)
+ return;
+
+ list_lru_destroy(&lru->global_lru);
+
+ mutex_lock(&memcg_create_mutex);
+ __memcg_list_lru_destroy(lru);
+ list_del(&lru->list);
+ mutex_unlock(&memcg_create_mutex);
+}
+
+struct list_lru *
+mem_cgroup_list_lru(struct memcg_list_lru *lru, struct mem_cgroup *memcg)
+{
+ struct list_lru **memcg_lrus;
+ struct list_lru *memcg_lru;
+ int memcg_id;
+
+ memcg_id = memcg_cache_id(memcg);
+ if (memcg_id < 0)
+ return &lru->global_lru;
+
+ rcu_read_lock();
+ memcg_lrus = rcu_dereference(lru->memcg_lrus);
+ memcg_lru = memcg_lrus[memcg_id];
+ rcu_read_unlock();
+
+ return memcg_lru;
+}
+
+struct list_lru *
+mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr)
+{
+ struct page *page = virt_to_page(ptr);
+ 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 mem_cgroup_list_lru(lru, memcg);
+}
#else
static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
{
@@ -6051,6 +6294,7 @@ 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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