linux-kernel - Re: [PATCH v5 3/4] mm: thp: use folio_batch to handle THP splitting in deferred_split

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Message-ID: <bfdc78de-febd-4224-94c7-bb02ee71aefe@linux.dev>
Date: Fri, 7 Nov 2025 10:52:10 +0800
From: Qi Zheng <qi.zheng@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>,
 Wei Yang <richard.weiyang@...il.com>
Cc: hannes@...xchg.org, hughd@...gle.com, mhocko@...e.com,
 roman.gushchin@...ux.dev, shakeel.butt@...ux.dev, muchun.song@...ux.dev,
 david@...hat.com, lorenzo.stoakes@...cle.com, ziy@...dia.com,
 harry.yoo@...cle.com, baolin.wang@...ux.alibaba.com,
 Liam.Howlett@...cle.com, npache@...hat.com, ryan.roberts@....com,
 dev.jain@....com, baohua@...nel.org, lance.yang@...ux.dev,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
 Muchun Song <songmuchun@...edance.com>, Qi Zheng <zhengqi.arch@...edance.com>
Subject: Re: [PATCH v5 3/4] mm: thp: use folio_batch to handle THP splitting
 in deferred_split_scan()



On 11/7/25 10:29 AM, Andrew Morton wrote:
> On Thu, 6 Nov 2025 14:52:13 +0000 Wei Yang <richard.weiyang@...il.com> wrote:
> 
>>> +		if (folio_order(folio) > 1) {
>>> +			if (!list_empty(&folio->_deferred_list)) {
>>> +				ds_queue->split_queue_len--;
>>> +				/*
>>> +				 * Reinitialize page_deferred_list after removing the
>>> +				 * page from the split_queue, otherwise a subsequent
>>> +				 * split will see list corruption when checking the
>>> +				 * page_deferred_list.
>>> +				 */
>>> +				list_del_init(&folio->_deferred_list);
>>> +			}
>>> 			if (folio_test_partially_mapped(folio)) {
>>> 				folio_clear_partially_mapped(folio);
>>> 				mod_mthp_stat(folio_order(folio),
>>> 					      MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
>>> 			}
>>> -			/*
>>> -			 * Reinitialize page_deferred_list after removing the
>>> -			 * page from the split_queue, otherwise a subsequent
>>> -			 * split will see list corruption when checking the
>>> -			 * page_deferred_list.
>>> -			 */
>>> -			list_del_init(&folio->_deferred_list);
>>
>> @Andrew
>>
>> Current mm-new looks not merge the code correctly?
>>
> 
> It happens.  We presently have 29 patches which alter mm/huge_memory.c.
> 
> Thanks for checking.  I'll drop version 5 of "reparent the THP split queue".
> 
> Please check what remains, and send a v6 against tomorrow's
> mm-new/mm-unstable.

OK, will rebase and resend it.