linux-kernel - Re: [PATCH] mm/vmscan: Fix hard LOCKUP in function isolate_lru

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Message-ID: <cafb20af-f152-9136-e762-901ce4dcf729@kylinos.cn>
Date: Wed, 25 Sep 2024 17:53:26 +0800
From: liuye <liuye@...inos.cn>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmscan: Fix hard LOCKUP in function isolate_lru_folios



On 2024/9/25 下午5:29, Andrew Morton wrote:
> On Wed, 25 Sep 2024 16:37:14 +0800 liuye <liuye@...inos.cn> wrote:
> 
>>
>>
>> On 2024/9/25 上午8:22, Andrew Morton wrote:
>>> On Wed, 14 Aug 2024 17:18:25 +0800 liuye <liuye@...inos.cn> wrote:
>>>
>>>> @@ -1669,10 +1670,12 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
>>>>  		nr_pages = folio_nr_pages(folio);
>>>>  		total_scan += nr_pages;
>>>>  
>>>> -		if (folio_zonenum(folio) > sc->reclaim_idx ||
>>>> -				skip_cma(folio, sc)) {
>>>> +		/* Using max_nr_skipped to prevent hard LOCKUP*/
>>>> +		if ((max_nr_skipped < SWAP_CLUSTER_MAX_SKIPPED) &&
>>>> +			(folio_zonenum(folio) > sc->reclaim_idx || skip_cma(folio, sc))) {
>>>>  			nr_skipped[folio_zonenum(folio)] += nr_pages;
>>>>  			move_to = &folios_skipped;
>>>> +			max_nr_skipped++;
>>>>  			goto move;
>>>
>>> This hunk is not applicable to current mainline.
>>>
>>
>> Please see the PATCH v2 in link [1], and the related discussion in link [2].
>> Then please explain why it is not applicable,thank you.
> 
> What I mean is that the patch doesn't apply.
> 
> Current mainline has
> 
> 		if (folio_zonenum(folio) > sc->reclaim_idx) {
> 			nr_skipped[folio_zonenum(folio)] += nr_pages;
> 			move_to = &folios_skipped;
> 			goto move;
> 		}
> 

PATCH v2 base on current mainline.

@@ -1650,9 +1651,12 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
 		nr_pages = folio_nr_pages(folio);
 		total_scan += nr_pages;
 
-		if (folio_zonenum(folio) > sc->reclaim_idx) {
+		/* Using max_nr_skipped to prevent hard LOCKUP*/
+		if (max_nr_skipped < SWAP_CLUSTER_MAX_SKIPPED &&
+		    (folio_zonenum(folio) > sc->reclaim_idx)) {
 			nr_skipped[folio_zonenum(folio)] += nr_pages;
 			move_to = &folios_skipped;
+			max_nr_skipped++;
 			goto move;
 		}