linux-kernel - Re: [PATCH] mm: remove lru_add_drain_all in alloc_contig

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Message-ID: <20210210142846.GE3636@localhost.localdomain>
Date:   Wed, 10 Feb 2021 15:28:46 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH] mm: remove lru_add_drain_all in alloc_contig_range

On Tue, Feb 09, 2021 at 09:50:48AM -0800, Minchan Kim wrote:
> __alloc_contig_migrate_range already has lru_add_drain_all call
> via migrate_prep. It's necessary to move LRU taget pages into
> LRU list to be able to isolated. However, lru_add_drain_all call
> after __alloc_contig_migrate_range is called is pointless.
> 
> This patch removes it.
> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>

I agree with Michal that the changelog could benefit from Vastimil's
clarification, so with that:

Reviewed-by: Oscar Salvador <osalvador@...e.de>

> ---
>  mm/page_alloc.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6446778cbc6b..f8fbee73dd6d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8603,8 +8603,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>  	 * isolated thus they won't get removed from buddy.
>  	 */
>  
> -	lru_add_drain_all();
> -
>  	order = 0;
>  	outer_start = start;
>  	while (!PageBuddy(pfn_to_page(outer_start))) {
> -- 
> 2.30.0.478.g8a0d178c01-goog
> 
> 

-- 
Oscar Salvador
SUSE L3