linux-kernel - Re: [PATCH] mm/page_isolation: do not isolate the max order page

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Date:   Thu, 3 Dec 2020 17:27:07 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Muchun Song <songmuchun@...edance.com>, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page_isolation: do not isolate the max order page

On 02.12.20 13:21, Muchun Song wrote:
> The max order page has no buddy page and never merge to other order.
> So isolating and then freeing it is pointless.
> 
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---
>  mm/page_isolation.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index a254e1f370a3..bddf788f45bf 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -88,7 +88,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
>  	 */
>  	if (PageBuddy(page)) {
>  		order = buddy_order(page);
> -		if (order >= pageblock_order) {
> +		if (order >= pageblock_order && order < MAX_ORDER - 1) {
>  			pfn = page_to_pfn(page);
>  			buddy_pfn = __find_buddy_pfn(pfn, order);
>  			buddy = page + (buddy_pfn - pfn);
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb