linux-kernel - Re: [PATCH] mm/mglru: Stop try_to_inc_min_seq() if the oldest generation LRU lists are not empty

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Message-ID: <CAJj2-QGgHSdzq5DqSi5M+XGeKWRD8aeH_C-OptyCDeV9CEHkBA@mail.gmail.com>
Date: Wed, 2 Jul 2025 12:22:28 -0700
From: Yuanchu Xie <yuanchu@...gle.com>
To: Hao Jia <jiahao.kernel@...il.com>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, yuzhao@...gle.com, 
	kinseyho@...gle.com, david@...hat.com, mhocko@...nel.org, 
	zhengqi.arch@...edance.com, shakeel.butt@...ux.dev, 
	lorenzo.stoakes@...cle.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Hao Jia <jiahao1@...iang.com>
Subject: Re: [PATCH] mm/mglru: Stop try_to_inc_min_seq() if the oldest
 generation LRU lists are not empty

On Tue, Jul 1, 2025 at 10:45 PM Hao Jia <jiahao.kernel@...il.com> wrote:
>
> Perhaps another way to explain it is clearer.
>
> It is known that min_seq[type] has not increased, that is, min_seq[type]
> is equal to lrugen->min_seq[type], then the following:
>
> case 1: min_seq[type] has not been reassigned and changed before
> judgment min_seq[type] <= lrugen->min_seq[type].
>
> Then the subsequent min_seq[type] <= lrugen->min_seq[type] judgment will
> always be true.
>
>
> case 2: min_seq[type] is reassigned to seq, before judgment
> min_seq[type] <= lrugen->min_seq[type].
>
> Then at least the condition of min_seq[type] > seq must be met before
> min_seq[type] will be reassigned to seq.
> That is to say, before the reassignment, lrugen->min_seq[type] > seq is
> met, and then min_seq[type] = seq.
>
> Then the following min_seq[type]（seq） <= lrugen->min_seq[type] judgment
> is always true.

This sounds good to me. Can you change the code to use one bool to
detect any increments in `min_seq[type]`? You don't need `int
seq_inc_flags[ANON_AND_FILE] = {0};`

Also update the commit message with what you have here. IMO much more clear.

Thanks,
Yuanchu