linux-kernel - Re: [PATCH 0/4] memcg: cleanup the memcg stats interfaces

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Message-ID: <b3ba7892-ed5e-45bb-9b1c-e901b622306d@linux.dev>
Date: Wed, 12 Nov 2025 10:11:11 +0800
From: Qi Zheng <qi.zheng@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Muchun Song <muchun.song@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
 cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 Meta kernel team <kernel-team@...a.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/4] memcg: cleanup the memcg stats interfaces



On 11/12/25 12:45 AM, Shakeel Butt wrote:
> On Tue, Nov 11, 2025 at 04:36:14PM +0800, Qi Zheng wrote:
>> Hi Shakeel,
>>
>> On 11/11/25 7:20 AM, Shakeel Butt wrote:
>>> The memcg stats are safe against irq (and nmi) context and thus does not
>>> require disabling irqs. However for some stats which are also maintained
>>> at node level, it is using irq unsafe interface and thus requiring the
>>> users to still disables irqs or use interfaces which explicitly disables
>>> irqs. Let's move memcg code to use irq safe node level stats function
>>> which is already optimized for architectures with HAVE_CMPXCHG_LOCAL
>>> (all major ones), so there will not be any performance penalty for its
>>> usage.
>>
>> Generally, places that call __mod_lruvec_state() also call
>> __mod_zone_page_state(), and it also has the corresponding optimized
>> version (mod_zone_page_state()). It seems necessary to clean that up
>> as well, so that those disabling-IRQs that are only used for updating
>> vmstat can be removed.
> 
> I agree, please take a stab at that.

OK, will do.