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Message-ID: <b7bca04e-0665-f80a-94b6-b8d857edfce1@bytedance.com>
Date:   Thu, 19 Oct 2023 16:22:38 +0800
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Subject: Re: [PATCH v2 2/2] mm: memory_hotplug: drop memoryless node from
 fallback lists
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To:     David Hildenbrand <david@redhat.com>
Cc:     akpm@linux-foundation.org, rppt@kernel.org, vbabka@suse.cz,
        mhocko@suse.com, willy@infradead.org, mgorman@techsingularity.net,
        mingo@kernel.org, aneesh.kumar@linux.ibm.com, ying.huang@intel.com,
        hannes@cmpxchg.org, osalvador@suse.de,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <cover.1697687357.git.zhengqi.arch@bytedance.com>
 <32c12381941f347ebafb9cb5bc9f0a4a535ff646.1697687357.git.zhengqi.arch@bytedance.com>
 <66e16a28-2d04-4b2c-88a8-692edf587f02@redhat.com>
From:   Qi Zheng <zhengqi.arch@bytedance.com>
In-Reply-To: <66e16a28-2d04-4b2c-88a8-692edf587f02@redhat.com>
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Hi David,

On 2023/10/19 16:11, David Hildenbrand wrote:
> On 19.10.23 09:36, Qi Zheng 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().
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.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 d4a364fdaf8f..18af399627f0 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -2036,12 +2036,12 @@ int __ref offline_pages(unsigned long 
>> start_pfn, unsigned long nr_pages,
>>       /* reinitialise watermarks and update pcp limits */
>>       init_per_zone_wmark_min();
>> +    node_states_clear_node(node, &arg);
>>       if (!populated_zone(zone)) {
>>           zone_pcp_reset(zone);
>>           build_all_zonelists(NULL);
>>       }
>> -    node_states_clear_node(node, &arg);
>>       if (arg.status_change_nid >= 0) {
>>           kcompactd_stop(node);
>>           kswapd_stop(node);
> 
> Probably worth a comment.
> 
> /*
>   * Make sure to mark the node as memory-less before rebuilding the zone
>   * list. Otherwise this node would still appear in the fallback lists.
>   */

OK, will add it in the v3.

> 
> Acked-by: David Hildenbrand <david@redhat.com>

Thanks.

>