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

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Message-ID: <706c6df4-4bd1-de52-f04f-8127d243bb89@bytedance.com>
Date:   Fri, 20 Oct 2023 17:10:49 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     Ingo Molnar <mingo@...nel.org>
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

Hi Ingo,

On 2023/10/20 16:32, Ingo Molnar wrote:
> 
> * 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

Will do.

> 
>>
>> 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.

> 
> Thanks,
> 
> 	Ingo