linux-kernel - Re: [PATCH v3 28/30 fix 1/2] mm: memcontrol: fix lruvec_stats->state

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] [day] [month] [year] [list]

Message-ID: <7c49e382-9f67-4a49-a884-47c96ab348d5@linux.dev>
Date: Wed, 21 Jan 2026 19:25:39 +0800
From: Qi Zheng <qi.zheng@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Muchun Song <muchun.song@...ux.dev>, hannes@...xchg.org,
 hughd@...gle.com, mhocko@...e.com, roman.gushchin@...ux.dev,
 david@...nel.org, lorenzo.stoakes@...cle.com, ziy@...dia.com,
 harry.yoo@...cle.com, yosry.ahmed@...ux.dev, imran.f.khan@...cle.com,
 kamalesh.babulal@...cle.com, axelrasmussen@...gle.com, yuanchu@...gle.com,
 weixugc@...gle.com, chenridong@...weicloud.com, mkoutny@...e.com,
 akpm@...ux-foundation.org, hamzamahfooz@...ux.microsoft.com,
 apais@...ux.microsoft.com, lance.yang@...ux.dev, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
 Qi Zheng <zhengqi.arch@...edance.com>
Subject: Re: [PATCH v3 28/30 fix 1/2] mm: memcontrol: fix
 lruvec_stats->state_local reparenting



On 1/21/26 4:20 PM, Shakeel Butt wrote:
> On Wed, Jan 21, 2026 at 11:43:50AM +0800, Qi Zheng wrote:
>>
>>
>> On 1/21/26 2:47 AM, Shakeel Butt wrote:
>>> On Tue, Jan 20, 2026 at 03:19:00PM +0800, Muchun Song wrote:
>>>>
>>>>
>>>>>> No reparenting local stats for v2.
>>>>>
>>>>> It seems that lruvec_stats->state_local (non-hierarchical) needs to be
>>>>> relocated in both v1 and v2.
>>>>
>>>> Here we might need to elaborate a bit. Specifically, in the function
>>>> `count_shadow_nodes`, the use of `lruvec_page_state_local` to obtain
>>>> LRU and SLAB pages seems to also require these logics to work correctly.
>>>> For SLAB, it appears that the statistics here have already been
>>>> problematic for a while since SLAB pages have been reparented, right?
>>>>
>>>
>>> Thanks a lot, now it is clear and yes it seems like SLAB is problematic
>>> but now I am wondering if it is really worth fixing. For LRU pages, how
>>> about using lruvec_lru_size() defined in vmscan.c. That would at least
>>> keep count_shadow_nodes() working irrespective of LRU reparenting.
>>
>> Do you mean calling lruvec_lru_size() in count_shadow_nodes()?
> 
> Yes but I am mainly brainstorming. We can keep the reparenting local

OK, I will take a closer look.

> stats for both v1 and v2 for now as it is not a performance critical
> path. I am more worried about the stats update path where upward
> traversal of memcg for CSS_DYING can be costly and I don't want that in
> v2.
> 
>> But
>> numa_stat interface also reads lruvec_stats->state and make it visible
>> to the user.
>>
> 
> Not sure how this is relevant.

My mistake, please ignore it.

Thanks!