Re: [PATCH RFC 1/2] mm: collect the number of anon large folios

[Ryan Roberts <ryan.roberts@arm.com>]

On 09/08/2024 09:58, David Hildenbrand wrote:
> On 09.08.24 10:42, David Hildenbrand wrote:
>>>> Not sure I fully understand why David prefers to do the unaccounting at
>>>> free-time though? It feels unbalanced to me to increment when first mapped but
>>>> decrement when freed. Surely its safer to either use alloc/free or use first
>>>> map/last map?
>>>>
>>>> If using alloc/free isn't there a THP constructor/destructor that prepares the
>>>> deferred list? (My memory may be failing me). Could we use that?
>>>
>>> Additionally, if we wanted to extend (eventually) to track the number of shmem
>>> and file mthps in additional counters, could we also account using similar folio
>>> free-time hooks? If not, it might be an argument to account in rmap_unmap to be
>>> consistent for all?
>>
>> Again, see NR_FILE_THPS handling. No rmap over-complication please.
> 
> ... not to mention that it is non-sensical to only count pageache folios that
> are mapped to user space ;)

Yes, good point. I'll get back in my box. :)