Re: [PATCH] support "THPeligible" semantics for mTHP with anonymous shmem

David Hildenbrand
2024-07-01T06:55:29Z

On 01.07.24 08:47, Baolin Wang wrote:
> CC Barry.
>
> On 2024/6/28 18:49, Bang Li wrote:
>> After the commit 7fb1b252afb5 ("mm: shmem: add mTHP support for
>> anonymous shmem"), we can configure different policies through
>> the multi-size THP sysfs interface for anonymous shmem. But
>> currently "THPeligible" indicates only whether the mapping is
>> eligible for allocating THP-pages as well as the THP is PMD
>> mappable or not for anonymous shmem, we need to support semantics
>> for mTHP with anonymous shmem similar to those for mTHP with
>> anonymous memory.
>
> I did not see a consensus that "THP*" related statistics should contain
> mTHP in previous discussion [1].
>
> In addition, if we all agree that "THPeligible" should include mTHP
> statistics, you should update the corresponding documentation to keep
> consistency.
>
> [1]
> https://lore.kernel.org/linux-mm/202406262300.iAURISyJ-lkp@intel.com/T/#md7a77056110cebcc2a9b3cd7e4a8d682667f6ba5
>

Fortunately, documentation (Documentation/filesystems/proc.rst) says:

"THPeligible" indicates whether the mapping is eligible for allocating
naturally aligned THP pages of any currently enabled size. 1 if true, 0
otherwise."

So that documentation is already pretty clear (we just have to make sure
the other ones are properly documented, for example as raised in reply
to [1]).

--
Cheers,

David / dhildenb