From: Yang Shi <shy828301@gmail.com>
To: guro@fb.com, ktkhai@virtuozzo.com, shakeelb@google.com,
david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com,
akpm@linux-foundation.org
Cc: shy828301@gmail.com, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [v2 PATCH 2/9] mm: memcontrol: use shrinker_rwsem to protect shrinker_maps allocation
Date: Mon, 14 Dec 2020 14:37:15 -0800 [thread overview]
Message-ID: <20201214223722.232537-3-shy828301@gmail.com> (raw)
In-Reply-To: <20201214223722.232537-1-shy828301@gmail.com>
Since memcg_shrinker_map_size just can be changd under holding shrinker_rwsem
exclusively, the read side can be protected by holding read lock, so it sounds
superfluous to have a dedicated mutex. This should not exacerbate the contention
to shrinker_rwsem since just one read side critical section is added.
Signed-off-by: Yang Shi <shy828301@gmail.com>
---
mm/internal.h | 1 +
mm/memcontrol.c | 17 +++++++----------
mm/vmscan.c | 2 +-
3 files changed, 9 insertions(+), 11 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index c43ccdddb0f6..10c79d199aaa 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -108,6 +108,7 @@ extern unsigned long highest_memmap_pfn;
/*
* in mm/vmscan.c:
*/
+extern struct rw_semaphore shrinker_rwsem;
extern int isolate_lru_page(struct page *page);
extern void putback_lru_page(struct page *page);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 29459a6ce1c7..ed942734235f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -394,8 +394,8 @@ DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key);
EXPORT_SYMBOL(memcg_kmem_enabled_key);
#endif
+/* It is only can be changed with holding shrinker_rwsem exclusively */
static int memcg_shrinker_map_size;
-static DEFINE_MUTEX(memcg_shrinker_map_mutex);
static void memcg_free_shrinker_map_rcu(struct rcu_head *head)
{
@@ -408,8 +408,6 @@ static int memcg_expand_one_shrinker_map(struct mem_cgroup *memcg,
struct memcg_shrinker_map *new, *old;
int nid;
- lockdep_assert_held(&memcg_shrinker_map_mutex);
-
for_each_node(nid) {
old = rcu_dereference_protected(
mem_cgroup_nodeinfo(memcg, nid)->shrinker_map, true);
@@ -458,7 +456,7 @@ static int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg)
if (mem_cgroup_is_root(memcg))
return 0;
- mutex_lock(&memcg_shrinker_map_mutex);
+ down_read(&shrinker_rwsem);
size = memcg_shrinker_map_size;
for_each_node(nid) {
map = kvzalloc_node(sizeof(*map) + size, GFP_KERNEL, nid);
@@ -469,7 +467,7 @@ static int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg)
}
rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, map);
}
- mutex_unlock(&memcg_shrinker_map_mutex);
+ up_read(&shrinker_rwsem);
return ret;
}
@@ -484,9 +482,8 @@ int memcg_expand_shrinker_maps(int new_id)
if (size <= old_size)
return 0;
- mutex_lock(&memcg_shrinker_map_mutex);
if (!root_mem_cgroup)
- goto unlock;
+ goto out;
for_each_mem_cgroup(memcg) {
if (mem_cgroup_is_root(memcg))
@@ -494,13 +491,13 @@ int memcg_expand_shrinker_maps(int new_id)
ret = memcg_expand_one_shrinker_map(memcg, size, old_size);
if (ret) {
mem_cgroup_iter_break(NULL, memcg);
- goto unlock;
+ goto out;
}
}
-unlock:
+out:
if (!ret)
memcg_shrinker_map_size = size;
- mutex_unlock(&memcg_shrinker_map_mutex);
+
return ret;
}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 48c06c48b97e..912c044301dd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -184,7 +184,7 @@ static void set_task_reclaim_state(struct task_struct *task,
}
static LIST_HEAD(shrinker_list);
-static DECLARE_RWSEM(shrinker_rwsem);
+DECLARE_RWSEM(shrinker_rwsem);
#ifdef CONFIG_MEMCG
/*
--
2.26.2
next prev parent reply other threads:[~2020-12-14 22:37 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-14 22:37 [RFC v2 PATCH 0/9] Make shrinker's nr_deferred memcg aware Yang Shi
2020-12-14 22:37 ` [v2 PATCH 1/9] mm: vmscan: use nid from shrink_control for tracepoint Yang Shi
2020-12-14 22:37 ` Yang Shi [this message]
2020-12-15 2:09 ` [v2 PATCH 2/9] mm: memcontrol: use shrinker_rwsem to protect shrinker_maps allocation Dave Chinner
2020-12-15 13:53 ` Johannes Weiner
2020-12-15 21:59 ` Dave Chinner
2020-12-16 13:17 ` Kirill Tkhai
2020-12-16 19:12 ` Johannes Weiner
2020-12-16 21:56 ` Yang Shi
2020-12-16 19:39 ` Roman Gushchin
2020-12-15 14:07 ` Johannes Weiner
2020-12-15 20:32 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 3/9] mm: vmscan: guarantee shrinker_slab_memcg() sees valid shrinker_maps for online memcg Yang Shi
2020-12-15 2:04 ` Dave Chinner
[not found] ` <20201215123802.GA379720@cmpxchg.org>
2020-12-15 12:58 ` Kirill Tkhai
2020-12-15 17:14 ` Johannes Weiner
[not found] ` <CAHbLzkrzv48S3ks-x8M=2sHxRS_+c-hLXdt4ScaWD6mC4ZFe8w@mail.gmail.com>
2020-12-28 20:03 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 4/9] mm: vmscan: use a new flag to indicate shrinker is registered Yang Shi
2020-12-14 22:37 ` [v2 PATCH 5/9] mm: memcontrol: add per memcg shrinker nr_deferred Yang Shi
2020-12-15 2:22 ` Dave Chinner
2020-12-15 14:45 ` Johannes Weiner
2020-12-15 21:57 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 6/9] mm: vmscan: use per memcg nr_deferred of shrinker Yang Shi
2020-12-15 2:46 ` Dave Chinner
2020-12-15 22:27 ` Yang Shi
2020-12-15 23:48 ` Dave Chinner
2020-12-14 22:37 ` [v2 PATCH 7/9] mm: vmscan: don't need allocate shrinker->nr_deferred for memcg aware shrinkers Yang Shi
2020-12-15 3:05 ` Dave Chinner
2020-12-15 23:07 ` Yang Shi
2020-12-18 0:56 ` Yang Shi
2020-12-18 1:09 ` Dave Chinner
2020-12-14 22:37 ` [v2 PATCH 8/9] mm: memcontrol: reparent nr_deferred when memcg offline Yang Shi
2020-12-15 3:07 ` Dave Chinner
2020-12-15 23:10 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 9/9] mm: vmscan: shrink deferred objects proportional to priority Yang Shi
2020-12-15 3:23 ` Dave Chinner
2020-12-15 23:59 ` Yang Shi
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