Re: [PATCH 03/17] mm/sparse-vmemmap: introduce folio-oriented vmemmap optimization macros

[Muchun Song <muchun.song@linux.dev>]

On 2026/7/15 13:08, Mike Rapoport wrote:
>> Introduce macros for those folio-oriented properties and use them to
>> replace the tail-based names in the HVO paths. This makes the code read
>> in terms of folio semantics instead of an implementation detail and
>> better matches other folio-based users such as DAX.
>>
>> No functional change intended.
>>
>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index bacd89572c5c..ea884245f499 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -107,13 +107,15 @@
>>   	 is_power_of_2(sizeof(struct page)) ? \
>>   	 MAX_FOLIO_NR_PAGES * sizeof(struct page) : 0)
>>   
>> -/*
>> - * vmemmap optimization (like HVO) is only possible for page orders that fill
>> - * two or more pages with struct pages.
>> - */
>> -#define VMEMMAP_TAIL_MIN_ORDER (ilog2(2 * PAGE_SIZE / sizeof(struct page)))
>> -#define __NR_VMEMMAP_TAILS (MAX_FOLIO_ORDER - VMEMMAP_TAIL_MIN_ORDER + 1)
>> -#define NR_VMEMMAP_TAILS (__NR_VMEMMAP_TAILS > 0 ? __NR_VMEMMAP_TAILS : 0)
>> +/* The number of vmemmap pages required by a vmemmap-optimized folio. */
>> +#define OPTIMIZED_FOLIO_VMEMMAP_PAGES		1
>> +#define OPTIMIZED_FOLIO_VMEMMAP_SIZE		(OPTIMIZED_FOLIO_VMEMMAP_PAGES * PAGE_SIZE)
>> +#define OPTIMIZED_FOLIO_VMEMMAP_NR_STRUCT_PAGES	(OPTIMIZED_FOLIO_VMEMMAP_SIZE / sizeof(struct page))
>> +#define OPTIMIZABLE_FOLIO_MIN_ORDER		(ilog2(OPTIMIZED_FOLIO_VMEMMAP_NR_STRUCT_PAGES) + 1)
>> +
>> +#define __NR_OPTIMIZABLE_FOLIO_ORDERS		(MAX_FOLIO_ORDER - OPTIMIZABLE_FOLIO_MIN_ORDER + 1)
>> +#define NR_OPTIMIZABLE_FOLIO_ORDERS		\
>> +	(__NR_OPTIMIZABLE_FOLIO_ORDERS > 0 ? __NR_OPTIMIZABLE_FOLIO_ORDERS : 0)
> I can't say I like the new names, they read like some folio optimization
> rather than vmemmap optimization.
>
> I think they should be namespaced with VMEMMAP_ or even
> VMEMMAP_OPTIMIZATION_ (or VMEMMAP_OPT_) and should not mention folio.

If you're okay with it, I'll update those macros to:

VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES
VMEMMAP_OPTIMIZATION_MIN_ORDER
VMEMMAP_OPTIMIZATION_NR_ORDERS

>
> I'd also drop intermediate defines OPTIMIZED_FOLIO_VMEMMAP_PAGES and
> OPTIMIZED_FOLIO_VMEMMAP_SIZE and use 1 and PAGE_SIZE directly.

OK. I'll not introduce OPTIMIZED_FOLIO_VMEMMAP_PAGES and
OPTIMIZED_FOLIO_VMEMMAP_SIZE

Muchun,
Thanks.