diff mbox series

[5/9] memcg: no refilling stock from obj_cgroup_release

Message ID 20250315174930.1769599-6-shakeel.butt@linux.dev (mailing list archive)
State New
Headers show
Series memcg: cleanup per-cpu stock | expand

Commit Message

Shakeel Butt March 15, 2025, 5:49 p.m. UTC 
obj_cgroup_release is called when all the references to the objcg have
been released i.e. no more memory objects are pointing to it. Most
probably objcg->memcg will be pointing to some ancestor memcg. In
obj_cgroup_release(), the kernel calls obj_cgroup_uncharge_pages() which
refills the local stock.

There is no need to refill the local stock with some ancestor memcg and
flush the local stock. Let's decouple obj_cgroup_release() from the
local stock by uncharging instead of refilling. One additional benefit
of this change is that it removes the requirement to only call
obj_cgroup_put() outside of local_lock.

Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/memcontrol.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

Comments

Roman Gushchin March 18, 2025, 1:06 a.m. UTC | #1 
On Sat, Mar 15, 2025 at 10:49:26AM -0700, Shakeel Butt wrote:
> obj_cgroup_release is called when all the references to the objcg have
> been released i.e. no more memory objects are pointing to it. Most
> probably objcg->memcg will be pointing to some ancestor memcg. In
> obj_cgroup_release(), the kernel calls obj_cgroup_uncharge_pages() which
> refills the local stock.
> 
> There is no need to refill the local stock with some ancestor memcg and
> flush the local stock. Let's decouple obj_cgroup_release() from the
> local stock by uncharging instead of refilling. One additional benefit
> of this change is that it removes the requirement to only call
> obj_cgroup_put() outside of local_lock.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>

Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
diff mbox series

Patch

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7054b0ebd207..83db180455a1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -129,8 +129,7 @@  bool mem_cgroup_kmem_disabled(void)
 	return cgroup_memory_nokmem;
 }
 
-static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg,
-				      unsigned int nr_pages);
+static void memcg_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages);
 
 static void obj_cgroup_release(struct percpu_ref *ref)
 {
@@ -163,8 +162,16 @@  static void obj_cgroup_release(struct percpu_ref *ref)
 	WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
 	nr_pages = nr_bytes >> PAGE_SHIFT;
 
-	if (nr_pages)
-		obj_cgroup_uncharge_pages(objcg, nr_pages);
+	if (nr_pages) {
+		struct mem_cgroup *memcg;
+
+		memcg = get_mem_cgroup_from_objcg(objcg);
+		mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages);
+		memcg1_account_kmem(memcg, -nr_pages);
+		if (!mem_cgroup_is_root(memcg))
+			memcg_uncharge(memcg, nr_pages);
+		css_put(&memcg->css);
+	}
 
 	spin_lock_irqsave(&objcg_lock, flags);
 	list_del(&objcg->list);