linux-kernel - Re: [PATCH v3 next 4/5] memcg: factor out stat(event)/stat_local(event

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Message-ID: <6daaf853-1283-42e6-bb0f-55d951edc925@huaweicloud.com>
Date: Tue, 21 Jan 2025 22:15:00 +0800
From: Chen Ridong <chenridong@...weicloud.com>
To: Johannes Weiner <hannes@...xchg.org>, Yosry Ahmed <yosryahmed@...gle.com>
Cc: akpm@...ux-foundation.org, mhocko@...nel.org, roman.gushchin@...ux.dev,
 shakeel.butt@...ux.dev, muchun.song@...ux.dev, davidf@...eo.com,
 vbabka@...e.cz, mkoutny@...e.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
 chenridong@...wei.com, wangweiyang2@...wei.com
Subject: Re: [PATCH v3 next 4/5] memcg: factor out
 stat(event)/stat_local(event_local) reading functions



On 2025/1/18 2:02, Johannes Weiner wrote:
> On Fri, Jan 17, 2025 at 09:01:59AM -0800, Yosry Ahmed wrote:
>> On Fri, Jan 17, 2025 at 8:56 AM Johannes Weiner <hannes@...xchg.org> wrote:
>>>
>>> On Fri, Jan 17, 2025 at 01:46:44AM +0000, Chen Ridong wrote:
>>>> From: Chen Ridong <chenridong@...wei.com>
>>>>
>>>> The only difference between 'lruvec_page_state' and
>>>> 'lruvec_page_state_local' is that they read 'state' and 'state_local',
>>>> respectively. Factor out an inner functions to make the code more concise.
>>>> Do the same for reading 'memcg_page_stat' and 'memcg_events'.
>>>>
>>>> Signed-off-by: Chen Ridong <chenridong@...wei.com>
>>>
>>> bool parameters make for poor readability at the callsites :(
>>>
>>> With the next patch moving most of the duplication to memcontrol-v1.c,
>>> I think it's probably not worth refactoring this.
>>
>> Arguably the duplication would now be across two different files,
>> making it more difficult to notice and keep the implementations in
>> sync.
> 
> Dependencies between the files is a bigger pain. E.g. try_charge()
> being defined in memcontrol-v1.h makes memcontrol.c more difficult to
> work with. That shared state also immediately bitrotted when charge
> moving was removed and the last cgroup1 caller disappeared.
> 
> The whole point of the cgroup1 split was to simplify cgroup2 code. The
> tiny amount of duplication in this case doesn't warrant further
> entanglement between the codebases.

Thank you for your review.

I agree with that. However, If I just move the 'local' functions to
memcontrol-v1.c, I have to move some dependent declarations to the
memcontrol-v1.h.
E.g. struct memcg_vmstats, MEMCG_VMSTAT_SIZE and so on.

Is this worth doing?

Best regards,
Ridong