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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c8d704f2-cc1c-52d2-3898-bf07dcb76e1a@redhat.com>
Date:   Mon, 7 Feb 2022 15:50:54 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     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 07.02.22 14:36, 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>
> ---
>  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))


Makes sense, although we just don't care about the CPU cycles at that point.

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

-- 
Thanks,

David / dhildenb