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Commit 2788cf0c authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
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memcg: reparent list_lrus and free kmemcg_id on css offline 



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: default avatarVladimir 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3f97b163

include/linux/list_lru.h

+2 −1
Original line number Diff line number Diff line
@@ -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

mm/list_lru.c

+43 −3
Original line number Diff line number Diff line
@@ -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)

{

mm/memcontrol.c

+34 −5
Original line number Diff line number Diff line
@@ -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)