linux-kernel - Re: [PATCH v3 3/3] mm/migrate: move common code to numa_migrate_check (was numa_migrate

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Message-ID: <87msliv5wd.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Mon, 12 Aug 2024 10:20:18 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: David Hildenbrand <david@...hat.com>
Cc: Zi Yan <ziy@...dia.com>,  linux-mm@...ck.org,  Andrew Morton
 <akpm@...ux-foundation.org>,  Baolin Wang <baolin.wang@...ux.alibaba.com>,
  Kefeng Wang <wangkefeng.wang@...wei.com>,  Yang Shi
 <shy828301@...il.com>,  Mel Gorman <mgorman@...e.de>,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] mm/migrate: move common code to
 numa_migrate_check (was numa_migrate_prep)

David Hildenbrand <david@...hat.com> writes:

> On 09.08.24 16:59, Zi Yan wrote:
>> do_numa_page() and do_huge_pmd_numa_page() share a lot of common code. To
>> reduce redundancy, move common code to numa_migrate_prep() and rename
>> the function to numa_migrate_check() to reflect its functionality.
>> Now do_huge_pmd_numa_page() also checks shared folios to set
>> TNF_SHARED flag.
>
> Yeah, I was also wondering why we didn't check that in the PMD case.

IIUC, before commit 728be28fae8c ("mm: migrate: remove THP mapcount
check in numamigrate_isolate_page()"), we don't allow to migrate THP
with mapcount > 1.  So, it's unnecessary to set TNF_SHARED flag at that
time.  However, after that commit, we need to do it.

--
Best Regards,
Huang, Ying