Re: [PATCH] mm/page_alloc: only search higher order when fallback

[Vlastimil Babka]

On 8/3/22 04:51, Abel Wu wrote:
> It seems unnecessary to search pages with order < alloc_order in
> fallback allocation.

This can currently happen with ALLOC_NOFRAGMENT and alloc_order >
pageblock_order, so add a test to prevent it.

> Signed-off-by: Abel Wu <wuyun.abel@xxxxxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e008a3df0485..0abafc2fc3e0 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2934,7 +2934,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
>  	 * i.e. orders < pageblock_order. If there are no local zones free,
>  	 * the zonelists will be reiterated without ALLOC_NOFRAGMENT.
>  	 */
> -	if (alloc_flags & ALLOC_NOFRAGMENT)
> +	if (order < pageblock_order && alloc_flags & ALLOC_NOFRAGMENT)
>  		min_order = pageblock_order;
>  
>  	/*