linux-kernel - Re: [PATCH v2 4/9] mm/vmscan: save a bit of stack space in shrink

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Message-ID: <84b6946b-01ed-bc40-9da5-f62bf2b6de90@huawei.com>
Date:   Tue, 12 Apr 2022 11:13:54 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     "ying.huang@...el.com" <ying.huang@...el.com>,
        <akpm@...ux-foundation.org>
CC:     <songmuchun@...edance.com>, <hch@...radead.org>,
        <willy@...radead.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/9] mm/vmscan: save a bit of stack space in
 shrink_lruvec

On 2022/4/12 8:57, ying.huang@...el.com wrote:
> On Sat, 2022-04-09 at 17:34 +0800, Miaohe Lin wrote:
>> LRU_UNEVICTABLE is not taken into account when shrink lruvec. So we can
>> save a bit of stack space by shrinking the array size of nr and targets
>> to NR_LRU_LISTS - 1. No functional change intended.
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>> ---
>>  mm/vmscan.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 59b96320f481..0e5818970998 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -2881,8 +2881,9 @@ static bool can_age_anon_pages(struct pglist_data *pgdat,
>>  
>>
>>  static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
>>  {
>> -	unsigned long nr[NR_LRU_LISTS];
>> -	unsigned long targets[NR_LRU_LISTS];
>> +	/* LRU_UNEVICTABLE is not taken into account. */
>> +	unsigned long nr[NR_LRU_LISTS - 1];
>> +	unsigned long targets[NR_LRU_LISTS - 1];
>>  	unsigned long nr_to_scan;
>>  	enum lru_list lru;
>>  	unsigned long nr_reclaimed = 0;
> 
> As Christoph pointed out, this is hacky without much benefit.  Please
> drop this patch.

Will drop this patch. Thanks.

> 
> Best Regards,
> Huang, Ying
> 
> .
>