Re: [PATCH v3 2/2] mm/mglru: fix ineffective memory protection for non-kswapd reclaim

[Ridong Chen <ridong.chen@linux.dev>]

On 9/3/2026 2:30 PM, Barry Song wrote:
> On Thu, Sep 3, 2026 at 11:20 AM Ridong Chen <ridong.chen@linux.dev> wrote:
>>
>> From: Ridong Chen <chenridong@xiaomi.com>
>>
>> For MGLRU, memory.min/low is not honored during global proactive reclaim
>> (writing to the root memory.reclaim) and global direct reclaim, because
>> these paths shrink memcgs using stale or effective protection (emin/elow).
> 
> Are you sure it should be “stale or effective”?
> My gut feeling is that we don't need the “or” here.
> 

My bad. It was a typo. Will remove "or".

> [...]
>>
>> Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
>> Cc: stable@vger.kernel.org
>> Assisted-by: Claude:claude-opus-4-8
>> Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
>> ---
> 
> With a few nits:
> 
> Reviewed-by: Barry Song <baohua@kernel.org>
> 
> [...]
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index b4c9b8f3dfe9..500cc2051d13 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -5111,7 +5111,13 @@ static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)
>>          struct mem_cgroup *memcg = lruvec_memcg(lruvec);
>>          struct pglist_data *pgdat = lruvec_pgdat(lruvec);
>>
>> -       /* lru_gen_age_node() called mem_cgroup_calculate_protection() */
>> +       /*
>> +        * For kswapd, lru_gen_age_node() has already called
>> +        * mem_cgroup_calculate_protection()
>> +        */
> 
> Could be clearer:
> 
> /*
>   * For kswapd, mem_cgroup_calculate_protection() has already
>   * been called during the top-down cgroup traversal.
>   */
> 

Thank you, will update.

>> +       if (!current_is_kswapd())
>> +               mem_cgroup_calculate_protection_path(NULL, memcg);
> 
> Best Regards
> Barry

-- 
Best regards
Ridong