Re: [RFC PATCH 5/5] mm: shmem: add anonymous share mTHP counters

[Lance Yang]

On 2024/4/23 09:17, Barry Song wrote:
[...]
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index 26b6fa98d8ac..67b9c1acad31 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -270,6 +270,8 @@ enum mthp_stat_item {
>>          MTHP_STAT_ANON_SWPOUT,
>>          MTHP_STAT_ANON_SWPOUT_FALLBACK,
>>          MTHP_STAT_ANON_SWPIN_REFAULT,
>> +       MTHP_STAT_SHMEM_ANON_ALLOC,
>> +       MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK,
> 
> not quite sure about this. for 2MB pmd-mapped THP shmem, we count them
> as FILE_THP.
> here we are counting as SHMEM_ANON. To me, SHMEM_ANON is more correct but
> it doesn't align with pmd-mapped THP. David, Ryan, what do you think?

+1

IMO, shmem isn't actually file-backed, but it has file-backed-like
characteristics :)

FWIW, perhaps MTHP_STAT_FILE_ALLOC and MTHP_STAT_FILE_ALLOC_FALLBACK
would better align with PMD/PTE-mapped THP.

Thanks,
Lance