linux-kernel - Re: [PATCH v7 2/2] mm/memory hotplug/unplug: Optimize zone->contiguous update when changes pfn range

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Message-ID: <6d2cda3f-7fe1-4436-9760-fde0622e88ad@intel.com>
Date: Thu, 8 Jan 2026 16:31:05 +0800
From: "Li, Tianyou" <tianyou.li@...el.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>, Oscar Salvador
	<osalvador@...e.de>, Mike Rapoport <rppt@...nel.org>, Wei Yang
	<richard.weiyang@...il.com>
CC: <linux-mm@...ck.org>, Yong Hu <yong.hu@...el.com>, Nanhai Zou
	<nanhai.zou@...el.com>, Yuan Liu <yuan1.liu@...el.com>, Tim Chen
	<tim.c.chen@...ux.intel.com>, Qiuxu Zhuo <qiuxu.zhuo@...el.com>, Yu C Chen
	<yu.c.chen@...el.com>, Pan Deng <pan.deng@...el.com>, Chen Zhang
	<zhangchen.kidd@...com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/2] mm/memory hotplug/unplug: Optimize
 zone->contiguous update when changes pfn range


On 1/7/2026 4:25 AM, David Hildenbrand (Red Hat) wrote:
>
> One more thing, the fact that the clear_zone_contiguous() happens in 
> move_pfn_range_to_zone() is a bit suboptimal.
>
> Maybe we need a comment here like
>
> /*
>  * Calculate the new zone contig state before move_pfn_range_to_zone()
>  * sets the zone temporarily to non-contiguous.
>  */
>
> Or something like that.
>
Will change accordingly. Thanks.


> Alternatively, we have to rework the code a bit that this dependency 
> is a bit clearer.


Agreed, probably we can have this optimization first then explore a more 
explicit approach for the zone contiguous state management.


>
>> +    new_contiguous_state = zone_contig_state_after_growing(zone, 
>> pfn, nr_pages);
>>         /* associate pfn range with the zone */
>>       move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_MOVABLE,
>> @@ -1204,7 +1273,7 @@ int online_pages(unsigned long pfn, unsigned 
>> long nr_pages,
>>       }
>>         online_pages_range(pfn, nr_pages);
>> -    set_zone_contiguous(zone);
>> +    set_zone_contiguous(zone, new_contiguous_state);
>>       adjust_present_page_count(pfn_to_page(pfn), group, nr_pages);
>

Regards,

Tianyou