linux-kernel - Re: [PATCH v3 2/2] mm: memory_hotplug: drop memoryless node from fallback lists

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Message-ID: <ZTI7DRNdObvSZXFG@gmail.com>
Date:   Fri, 20 Oct 2023 10:32:13 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Qi Zheng <zhengqi.arch@...edance.com>
Cc:     akpm@...ux-foundation.org, rppt@...nel.org, david@...hat.com,
        vbabka@...e.cz, mhocko@...e.com, willy@...radead.org,
        mgorman@...hsingularity.net, aneesh.kumar@...ux.ibm.com,
        ying.huang@...el.com, hannes@...xchg.org, osalvador@...e.de,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 2/2] mm: memory_hotplug: drop memoryless node from
 fallback lists


* Qi Zheng <zhengqi.arch@...edance.com> wrote:

> In offline_pages(), if a node becomes memoryless, we
> will clear its N_MEMORY state by calling node_states_clear_node().
> But we do this after rebuilding the zonelists by calling
> build_all_zonelists(), which will cause this memoryless node to
> still be in the fallback list of other nodes. This will incur
> some runtime overhead.
> 
> To drop memoryless node from fallback lists in this case, just
> call node_states_clear_node() before calling build_all_zonelists().

s/memoryless node
 /memoryless nodes

> 
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/memory_hotplug.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index d4a364fdaf8f..f019f7d6272c 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -2036,12 +2036,16 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
>  	/* reinitialise watermarks and update pcp limits */
>  	init_per_zone_wmark_min();
>  
> +	/*
> +	 * Make sure to mark the node as memory-less before rebuilding the zone
> +	 * list. Otherwise this node would still appear in the fallback lists.
> +	 */
> +	node_states_clear_node(node, &arg);

Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo