linux-kernel - Re: [PATCH v3 1/2] mm: huge_memory: disallow hugepages if the system-wide THP sysfs settings are disabled

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Message-ID: <ae78feb2-d044-41ba-bc4f-e3085428bc10@linux.alibaba.com>
Date: Tue, 24 Jun 2025 09:48:52 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
 hughd@...gle.com
Cc: ziy@...dia.com, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com,
 npache@...hat.com, ryan.roberts@....com, dev.jain@....com,
 baohua@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] mm: huge_memory: disallow hugepages if the
 system-wide THP sysfs settings are disabled



On 2025/6/23 21:54, David Hildenbrand wrote:
> 
>> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/ 
>> selftests/mm/khugepaged.c
>> index 4341ce6b3b38..85bfff53dba6 100644
>> --- a/tools/testing/selftests/mm/khugepaged.c
>> +++ b/tools/testing/selftests/mm/khugepaged.c
>> @@ -501,11 +501,7 @@ static void __madvise_collapse(const char *msg, 
>> char *p, int nr_hpages,
>>       printf("%s...", msg);
>> -    /*
>> -     * Prevent khugepaged interference and tests that MADV_COLLAPSE
>> -     * ignores /sys/kernel/mm/transparent_hugepage/enabled
>> -     */
>> -    settings.thp_enabled = THP_NEVER;
>> +    settings.thp_enabled = THP_ALWAYS;
> 
> 
> Would MADVISE mode also work here? If we don't set MADV_HUGEPAGE, then 
> khugepaged should be excluded, correct?

I tried this, but some test cases failed. As I replied to Barry, it's 
because some tests previously set MADV_NOHUGEPAGE, and now there is no 
way to clear the MADV_NOHUGEPAGE flag except by setting MADV_HUGEPAGE.