linux-kernel - Re: [PATCH 2/5] mm/vmscan: remove misleading setting to sc->priority

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Date:   Mon, 12 Jul 2021 19:10:03 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Michal Hocko <mhocko@...e.com>
CC:     <akpm@...ux-foundation.org>, <hannes@...xchg.org>,
        <vbabka@...e.cz>, <axboe@...nel.dk>, <iamjoonsoo.kim@....com>,
        <alexs@...nel.org>, <apopple@...dia.com>, <willy@...radead.org>,
        <minchan@...nel.org>, <david@...hat.com>, <shli@...com>,
        <hillf.zj@...baba-inc.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] mm/vmscan: remove misleading setting to sc->priority

On 2021/7/12 15:24, Michal Hocko wrote:
> On Sat 10-07-21 18:03:26, Miaohe Lin wrote:
>> The priority field of sc is used to control how many pages we should scan
>> at once while we always traverse the list to shrink the pages in these
>> functions. So these settings are unneeded and misleading.
> 
> I dunno. I agree that priority is not really used as these operate on
> page lists but I am not sure this is worth touching.

When I investigated the vmscan code, I thought the order here would control the
proportion of the pages in the list to shrink. So I prefer to remove these.

Thanks a lot for review and reply!

> 
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>> ---
>>  mm/vmscan.c | 2 --
>>  1 file changed, 2 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 6483fe0e2065..fbe53e60b248 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1702,7 +1702,6 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
>>  {
>>  	struct scan_control sc = {
>>  		.gfp_mask = GFP_KERNEL,
>> -		.priority = DEF_PRIORITY,
>>  		.may_unmap = 1,
>>  	};
>>  	struct reclaim_stat stat;
>> @@ -2327,7 +2326,6 @@ unsigned long reclaim_pages(struct list_head *page_list)
>>  	unsigned int noreclaim_flag;
>>  	struct scan_control sc = {
>>  		.gfp_mask = GFP_KERNEL,
>> -		.priority = DEF_PRIORITY,
>>  		.may_writepage = 1,
>>  		.may_unmap = 1,
>>  		.may_swap = 1,
>> -- 
>> 2.23.0
>