linux-kernel - Re: [RFC PATCH 05/10] memcg: no refilling stock from obj_cgroup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1058dae6-c89b-45ad-83c1-d903fd9532ae@suse.cz>
Date: Fri, 14 Mar 2025 11:09:55 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Shakeel Butt <shakeel.butt@...ux.dev>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Muchun Song <muchun.song@...ux.dev>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, linux-mm@...ck.org,
 cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 Meta kernel team <kernel-team@...a.com>
Subject: Re: [RFC PATCH 05/10] memcg: no refilling stock from
 obj_cgroup_release

On 3/14/25 07:15, Shakeel Butt wrote:
> obj_cgroup_release is called when all the references to the objcg has
> been released i.e. no more memory objects are pointing to it. Most
> probably objcg->memcg will be pointing to some ancestor memcg and at the
> moment, in obj_cgroup_release, the kernel call
> obj_cgroup_uncharge_pages() to uncharge last remaining memory.
> 
> However obj_cgroup_uncharge_pages() refills the local stock. There is
> no need to refill the local stock with some ancestor memcg and flush the
> local stock. In addition this removes the requirement to only call
> obj_cgroup_put() outside of local_lock.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/memcontrol.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> 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);