From b6d0471117daec360bad2b881c1e2d0f4d2c4d3b Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Thu, 3 Apr 2025 18:39:09 -0700 Subject: [PATCH] memcg: no refilling stock from obj_cgroup_release 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. Link: https://lkml.kernel.org/r/20250404013913.1663035-6-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Acked-by: Vlastimil Babka Reviewed-by: Roman Gushchin Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Sebastian Andrzej Siewior Signed-off-by: Andrew Morton --- mm/memcontrol.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 03a2be6d4a677..df52084e90f46 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); + mem_cgroup_put(memcg); + } spin_lock_irqsave(&objcg_lock, flags); list_del(&objcg->list); -- 2.50.1