From: Muchun Song <songmuchun@bytedance.com>
To: guro@fb.com, hannes@cmpxchg.org, mhocko@kernel.org,
akpm@linux-foundation.org, shakeelb@google.com,
vdavydov.dev@gmail.com
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
duanxiongchun@bytedance.com, fam.zheng@bytedance.com,
bsingharora@gmail.com, shy828301@gmail.com,
alex.shi@linux.alibaba.com,
Muchun Song <songmuchun@bytedance.com>
Subject: [RFC PATCH v2 05/18] mm: memcontrol: simplify the logic of objcg pinning memcg
Date: Fri, 9 Apr 2021 20:29:46 +0800 [thread overview]
Message-ID: <20210409122959.82264-6-songmuchun@bytedance.com> (raw)
In-Reply-To: <20210409122959.82264-1-songmuchun@bytedance.com>
The obj_cgroup_release() and memcg_reparent_objcgs() are serialized by
the css_set_lock. We do not need to care about objcg->memcg being
released in the process of obj_cgroup_release(). So there is no need
to pin memcg before releasing objcg. Remove those pinning logic to
simplfy the code.
There are only two places that modifies the objcg->memcg. One is the
initialization to objcg->memcg in the memcg_online_kmem(), another
is objcgs reparenting in the memcg_reparent_objcgs(). It is also
impossible for the two to run in parallel. So xchg() is unnecessary
and it is enough to use WRITE_ONCE().
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
mm/memcontrol.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1f807448233e..90c1ac58c64c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -261,7 +261,6 @@ static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg,
static void obj_cgroup_release(struct percpu_ref *ref)
{
struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt);
- struct mem_cgroup *memcg;
unsigned int nr_bytes;
unsigned int nr_pages;
unsigned long flags;
@@ -291,11 +290,9 @@ static void obj_cgroup_release(struct percpu_ref *ref)
nr_pages = nr_bytes >> PAGE_SHIFT;
spin_lock_irqsave(&css_set_lock, flags);
- memcg = obj_cgroup_memcg(objcg);
if (nr_pages)
obj_cgroup_uncharge_pages(objcg, nr_pages);
list_del(&objcg->list);
- mem_cgroup_put(memcg);
spin_unlock_irqrestore(&css_set_lock, flags);
percpu_ref_exit(ref);
@@ -330,17 +327,14 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg,
spin_lock_irq(&css_set_lock);
- /* Move active objcg to the parent's list */
- xchg(&objcg->memcg, parent);
- css_get(&parent->css);
- list_add(&objcg->list, &parent->objcg_list);
+ /* 1) Ready to reparent active objcg. */
+ list_add(&objcg->list, &memcg->objcg_list);
- /* Move already reparented objcgs to the parent's list */
- list_for_each_entry(iter, &memcg->objcg_list, list) {
- css_get(&parent->css);
- xchg(&iter->memcg, parent);
- css_put(&memcg->css);
- }
+ /* 2) Reparent active objcg and already reparented objcgs to parent. */
+ list_for_each_entry(iter, &memcg->objcg_list, list)
+ WRITE_ONCE(iter->memcg, parent);
+
+ /* 3) Move already reparented objcgs to the parent's list */
list_splice(&memcg->objcg_list, &parent->objcg_list);
spin_unlock_irq(&css_set_lock);
--
2.11.0
next prev parent reply other threads:[~2021-04-09 12:32 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-09 12:29 [RFC PATCH v2 00/18] Use obj_cgroup APIs to charge the LRU pages Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 01/18] mm: memcontrol: fix page charging in page replacement Muchun Song
2021-04-10 17:44 ` Shakeel Butt
2021-04-09 12:29 ` [RFC PATCH v2 02/18] mm: memcontrol: bail out early when !mm in get_mem_cgroup_from_mm Muchun Song
2021-04-10 17:47 ` Shakeel Butt
2021-04-09 12:29 ` Muchun Song [this message]
2021-04-09 16:27 ` [RFC PATCH v2 05/18] mm: memcontrol: simplify the logic of objcg pinning memcg Johannes Weiner
2021-04-09 12:29 ` [RFC PATCH v2 07/18] mm: memcontrol: introduce compact_lock_page_lruvec_irqsave Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 09/18] mm: vmscan: remove noinline_for_stack Muchun Song
2021-04-09 18:31 ` Johannes Weiner
2021-04-10 4:33 ` [External] " Muchun Song
2021-04-10 17:48 ` Shakeel Butt
2021-04-10 0:49 ` Roman Gushchin
2021-04-09 12:29 ` [RFC PATCH v2 10/18] mm: vmscan: rework move_pages_to_lru() Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 12/18] mm: thp: make deferred split queue lock safe when the LRU pages reparented Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 14/18] mm: memcontrol: introduce memcg_reparent_ops Muchun Song
[not found] ` <20210409122959.82264-5-songmuchun@bytedance.com>
2021-04-09 16:00 ` [RFC PATCH v2 04/18] mm: memcontrol: simplify lruvec_holds_page_lru_lock Johannes Weiner
2021-04-11 5:37 ` [External] " Muchun Song
[not found] ` <20210409122959.82264-7-songmuchun@bytedance.com>
2021-04-09 16:56 ` [RFC PATCH v2 06/18] mm: memcontrol: move the objcg infrastructure out of CONFIG_MEMCG_KMEM Johannes Weiner
2021-04-11 6:24 ` [External] " Muchun Song
2021-04-10 1:29 ` [RFC PATCH v2 00/18] Use obj_cgroup APIs to charge the LRU pages Roman Gushchin
2021-04-12 17:14 ` Johannes Weiner
2021-04-12 17:45 ` Roman Gushchin
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