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: <7f747869-dc37-64f3-127a-0b61a9d069dc@gmail.com>
Date: Thu, 3 Jul 2025 10:44:13 +0800
From: Hao Jia <jiahao.kernel@...il.com>
To: Yuanchu Xie <yuanchu@...gle.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 2025/7/3 03:22, Yuanchu Xie wrote:
> 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 for your review, I have done it in patch v2.

Link to v2:
https://lore.kernel.org/all/20250703023946.65315-1-jiahao.kernel@gmail.com/

Thanks,
Hao