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Message-ID: <95531f88-a1bd-3347-dc60-8e16de811145@redhat.com>
Date:   Wed, 21 Jun 2023 13:18:00 +0200
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Subject: Re: [PATCH v2] mm/min_free_kbytes: modify min_free_kbytes calculation
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To:     liuq <liuq131@chinatelecom.cn>, akpm@linux-foundation.org
Cc:     ying.huang@intel.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <20230621073912.21747-1-liuq131@chinatelecom.cn>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20230621073912.21747-1-liuq131@chinatelecom.cn>
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On 21.06.23 09:39, liuq wrote:
> The current calculation of min_free_kbytes only uses ZONE_DMA and
> ZONE_NORMAL pages,but the ZONE_MOVABLE zone->_watermark[WMARK_MIN]
> will also divide part of min_free_kbytes.This will cause the min
> watermark of ZONE_NORMAL to be too small in the presence of ZONE_MOVEABLE.
> 
> __GFP_HIGH and PF_MEMALLOC allocations usually don't need moveable
> zone pages, so just like ZONE_HIGHMEM, cap pages_min to a small
> value in __setup_per_zone_wmarks.
> 
> Signed-off-by: liuq <liuq131@chinatelecom.cn>
> ---
>   mm/page_alloc.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 47421bedc12b..608384712a89 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6364,7 +6364,7 @@ static void __setup_per_zone_wmarks(void)
>   
>   	/* Calculate total number of !ZONE_HIGHMEM pages */
>   	for_each_zone(zone) {
> -		if (!is_highmem(zone))
> +		if (!is_highmem(zone) || zone_idx(zone) != ZONE_MOVABLE)
>   			lowmem_pages += zone_managed_pages(zone);
>   	}
>   
> @@ -6374,7 +6374,7 @@ static void __setup_per_zone_wmarks(void)
>   		spin_lock_irqsave(&zone->lock, flags);
>   		tmp = (u64)pages_min * zone_managed_pages(zone);
>   		do_div(tmp, lowmem_pages);
> -		if (is_highmem(zone)) {
> +		if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) {
>   			/*
>   			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
>   			 * need highmem pages, so cap pages_min to a small

Patch subject should probably be something like

"mm/page_alloc: fix min_free_kbytes calculation regarding ZONE_MOVABLE"

?

-- 
Cheers,

David / dhildenb