linux-kernel - Re: [PATCH 2/4] mm/memory_hotplug: avoid calling zone_intersects() for ZONE

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Message-ID: <YgJAkJfEffpsmEuj@localhost.localdomain>
Date:   Tue, 8 Feb 2022 11:06:08 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] mm/memory_hotplug: avoid calling zone_intersects()
 for ZONE_NORMAL

On Mon, Feb 07, 2022 at 09:36:41PM +0800, Miaohe Lin wrote:
> If zid reaches ZONE_NORMAL, the caller will always get the NORMAL zone no
> matter what zone_intersects() returns. So we can save some possible cpu
> cycles by avoid calling zone_intersects() for ZONE_NORMAL.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

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

> ---
>  mm/memory_hotplug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index cbc67c27e0dd..140809e60e9a 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -826,7 +826,7 @@ static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn
>  	struct pglist_data *pgdat = NODE_DATA(nid);
>  	int zid;
>  
> -	for (zid = 0; zid <= ZONE_NORMAL; zid++) {
> +	for (zid = 0; zid < ZONE_NORMAL; zid++) {
>  		struct zone *zone = &pgdat->node_zones[zid];
>  
>  		if (zone_intersects(zone, start_pfn, nr_pages))
> -- 
> 2.23.0
> 
> 

-- 
Oscar Salvador
SUSE Labs