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

Bang Li
2024-07-01T08:23:01Z

Hi David,

On 2024/7/1 14:55, David Hildenbrand wrote:
> 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]).
>

Thanks for the clarification.

Thanks,
Bang