linux-kernel - Re: [RFC PATCH] mm: fix the inaccurate memory statistics issue for users

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Message-ID: <99e39ac1-d766-4d6e-a69a-525c49662ac0@linux.alibaba.com>
Date: Sat, 24 May 2025 09:29:16 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: SeongJae Park <sj@...nel.org>
Cc: akpm@...ux-foundation.org, david@...hat.com, lorenzo.stoakes@...cle.com,
 Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com,
 mhocko@...e.com, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, shakeel.butt@...ux.dev
Subject: Re: [RFC PATCH] mm: fix the inaccurate memory statistics issue for
 users



On 2025/5/24 01:23, SeongJae Park wrote:
> On Fri, 23 May 2025 10:20:29 -0700 SeongJae Park <sj@...nel.org> wrote:
> 
>> On Fri, 23 May 2025 11:16:13 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:
>>
>>> On some large machines with a high number of CPUs running a 64K kernel,
>>
>> What does 64K kernel means?

Sorry for not being clear. I mean a 64K pagesize kernel on Arm servers.

>>> we found that the 'RES' field is always 0 displayed by the top command
>>> for some processes, which will cause a lot of confusion for users.
>>>
>>>      PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
>>>   875525 root      20   0   12480      0      0 R   0.3   0.0   0:00.08 top
>>>        1 root      20   0  172800      0      0 S   0.0   0.0   0:04.52 systemd
>>>
>>> The main reason is that the batch size of the percpu counter is quite large
>>> on these machines, caching a significant percpu value, since converting mm's
>>> rss stats into percpu_counter by commit f1a7941243c1 ("mm: convert mm's rss
>>> stats into percpu_counter").
> 
> Forgot asking this, sorry.  Should we add Fixes: tag and Cc stable@?

Yes, will add the Fixes tag in next version. Thanks for reviewing.