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memcg: reparent list_lrus and free kmemcg_id on css offline

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Now, the only reason to keep kmemcg_id till css free is list_lru, which
uses it to distribute elements between per-memcg lists.  However, it can
be easily sorted out - we only need to change kmemcg_id of an offline
cgroup to its parent's id, making further list_lru_add()'s add elements to
the parent's list, and then move all elements from the offline cgroup's
list to the one of its parent.  It will work, because a racing
list_lru_del() does not need to know the list it is deleting the element
from.  It can decrement the wrong nr_items counter though, but the ongoing
reparenting will fix it.  After list_lru reparenting is done we are free
to release kmemcg_id saving a valuable slot in a per-memcg array for new
cgroups.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vladimir Davydov 2015-02-12 14:59:38 -08:00 committed by Linus Torvalds
parent 3f97b16320
commit 2788cf0c40
3 changed files with 79 additions and 9 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
include/linux/list_lru.h
View file

@ -26,7 +26,7 @@ enum lru_status {
struct list_lru_one {
struct list_head list;
/* kept as signed so we can catch imbalance bugs */
/* may become negative during memcg reparenting */
long nr_items;
};
@ -62,6 +62,7 @@ int __list_lru_init(struct list_lru *lru, bool memcg_aware,
#define list_lru_init_memcg(lru) __list_lru_init((lru), true, NULL)
int memcg_update_all_list_lrus(int num_memcgs);
void memcg_drain_all_list_lrus(int src_idx, int dst_idx);
/**
* list_lru_add: add an element to the lru list's tail

46
mm/list_lru.c
View file

@ -100,7 +100,6 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
spin_lock(&nlru->lock);
l = list_lru_from_kmem(nlru, item);
WARN_ON_ONCE(l->nr_items < 0);
if (list_empty(item)) {
list_add_tail(item, &l->list);
l->nr_items++;
@ -123,7 +122,6 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item)
if (!list_empty(item)) {
list_del_init(item);
l->nr_items--;
WARN_ON_ONCE(l->nr_items < 0);
spin_unlock(&nlru->lock);
return true;
}
@ -156,7 +154,6 @@ static unsigned long __list_lru_count_one(struct list_lru *lru,
spin_lock(&nlru->lock);
l = list_lru_from_memcg_idx(nlru, memcg_idx);
WARN_ON_ONCE(l->nr_items < 0);
count = l->nr_items;
spin_unlock(&nlru->lock);
@ -458,6 +455,49 @@ int memcg_update_all_list_lrus(int new_size)
memcg_cancel_update_list_lru(lru, old_size, new_size);
goto out;
}
static void memcg_drain_list_lru_node(struct list_lru_node *nlru,
int src_idx, int dst_idx)
{
struct list_lru_one *src, *dst;
/*
* Since list_lru_{add,del} may be called under an IRQ-safe lock,
* we have to use IRQ-safe primitives here to avoid deadlock.
*/
spin_lock_irq(&nlru->lock);
src = list_lru_from_memcg_idx(nlru, src_idx);
dst = list_lru_from_memcg_idx(nlru, dst_idx);
list_splice_init(&src->list, &dst->list);
dst->nr_items += src->nr_items;
src->nr_items = 0;
spin_unlock_irq(&nlru->lock);
}
static void memcg_drain_list_lru(struct list_lru *lru,
int src_idx, int dst_idx)
{
int i;
if (!list_lru_memcg_aware(lru))
return;
for (i = 0; i < nr_node_ids; i++)
memcg_drain_list_lru_node(&lru->node[i], src_idx, dst_idx);
}
void memcg_drain_all_list_lrus(int src_idx, int dst_idx)
{
struct list_lru *lru;
mutex_lock(&list_lrus_mutex);
list_for_each_entry(lru, &list_lrus, list)
memcg_drain_list_lru(lru, src_idx, dst_idx);
mutex_unlock(&list_lrus_mutex);
}
#else
static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
{

39
mm/memcontrol.c
View file

@ -334,6 +334,7 @@ struct mem_cgroup {
#if defined(CONFIG_MEMCG_KMEM)
/* Index in the kmem_cache->memcg_params.memcg_caches array */
int kmemcg_id;
bool kmem_acct_activated;
bool kmem_acct_active;
#endif
@ -582,14 +583,10 @@ void memcg_put_cache_ids(void)
struct static_key memcg_kmem_enabled_key;
EXPORT_SYMBOL(memcg_kmem_enabled_key);
static void memcg_free_cache_id(int id);
static void disarm_kmem_keys(struct mem_cgroup *memcg)
{
if (memcg->kmemcg_id >= 0) {
if (memcg->kmem_acct_activated)
static_key_slow_dec(&memcg_kmem_enabled_key);
memcg_free_cache_id(memcg->kmemcg_id);
}
/*
* This check can't live in kmem destruction function,
* since the charges will outlive the cgroup
@ -3322,6 +3319,7 @@ static int memcg_activate_kmem(struct mem_cgroup *memcg,
int memcg_id;
BUG_ON(memcg->kmemcg_id >= 0);
BUG_ON(memcg->kmem_acct_activated);
BUG_ON(memcg->kmem_acct_active);
/*
@ -3365,6 +3363,7 @@ static int memcg_activate_kmem(struct mem_cgroup *memcg,
* patched.
*/
memcg->kmemcg_id = memcg_id;
memcg->kmem_acct_activated = true;
memcg->kmem_acct_active = true;
out:
return err;
@ -4047,6 +4046,10 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
{
struct cgroup_subsys_state *css;
struct mem_cgroup *parent, *child;
int kmemcg_id;
if (!memcg->kmem_acct_active)
return;
@ -4059,6 +4062,32 @@ static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
memcg->kmem_acct_active = false;
memcg_deactivate_kmem_caches(memcg);
kmemcg_id = memcg->kmemcg_id;
BUG_ON(kmemcg_id < 0);
parent = parent_mem_cgroup(memcg);
if (!parent)
parent = root_mem_cgroup;
/*
* Change kmemcg_id of this cgroup and all its descendants to the
* parent's id, and then move all entries from this cgroup's list_lrus
* to ones of the parent. After we have finished, all list_lrus
* corresponding to this cgroup are guaranteed to remain empty. The
* ordering is imposed by list_lru_node->lock taken by
* memcg_drain_all_list_lrus().
*/
css_for_each_descendant_pre(css, &memcg->css) {
child = mem_cgroup_from_css(css);
BUG_ON(child->kmemcg_id != kmemcg_id);
child->kmemcg_id = parent->kmemcg_id;
if (!memcg->use_hierarchy)
break;
}
memcg_drain_all_list_lrus(kmemcg_id, parent->kmemcg_id);
memcg_free_cache_id(kmemcg_id);
}
static void memcg_destroy_kmem(struct mem_cgroup *memcg)