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

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 2025/6/24 16:29, David Hildenbrand wrote:
> On 24.06.25 03:48, Baolin Wang wrote:
>>
>>
>> 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.
> 
> Okay, can you add that detail to the patch description. 

Sure. Will do.

> I suspect we 
> really want a way to undo what MADV_NOHUGEPAGE/MADV_NOHUGEPAGE did (if 
> only naming wouldn't be complicated: MADV_DEFAULT_HUGEPAGE, hmmmm).