Re: [PATCH 3/5] mm: add static huge zero folio

[David Hildenbrand <david@redhat.com>]

On 06.08.25 14:43, Pankaj Raghav (Samsung) wrote:
> On Wed, Aug 06, 2025 at 02:36:51PM +0200, David Hildenbrand wrote:
>> On 06.08.25 14:28, Pankaj Raghav (Samsung) wrote:
>>> On Wed, Aug 06, 2025 at 02:24:28PM +0200, David Hildenbrand wrote:
>>>> On 06.08.25 14:18, Pankaj Raghav (Samsung) wrote:
>>>>>> We could go one step further and special case in mm_get_huge_zero_folio() +
>>>>>> mm_put_huge_zero_folio() on CONFIG_STATIC_HUGE_ZERO_FOLIO.
>>>>>>
>>>>>
>>>>> Hmm, but we could have also failed to allocate even though the option
>>>>> was enabled.
>>>>
>>>> Then we return huge_zero_folio, which is NULL?
>>>>
>>>> Or what are you concerned about?
>>>
>>> But don't we want to keep the "dynamic" allocation part be present even
>>> though we failed to allocate it statically in the shrinker_init?
>>>
>>> Mainly so that the existing users of mm_get_huge_zero_folio() are not affected by
>>> these changes.
>>
>> I would just keep it simple and say that if we fail the early allocation
>> (which will be extremely unlikely that early during boot!), just don't ever
>> try to reallocate, even not when we could through mm_get_huge_zero_folio().
>>
>> That sounds as simple as it gets. Again, failing to allocate that early and
>> then succeeding to allocate later is a fairly unlikely scenario.
> 
> Ok. I will also document this as a comment just so that people are aware of
> this behaviour.
> 
> Thanks a lot David for the comments and feedback!

Sure, as always, feel free to object if you think I am talking nonsense :)

-- 
Cheers,

David / dhildenb