Re: [PATCH mm-unstable v18 11/14] mm/khugepaged: Introduce mTHP collapse support

[Nico Pache]

On 6/1/26 7:15 AM, David Hildenbrand (Arm) wrote:
>>>
>>> Reading this, it is unclear why exactly do we need the stack.
>>
>> So I looked into your items below. It seems logical, and I think it
>> works the same way; however, your method seems slightly harder to
>> understand due to all the edge cases and more error-prone to future
>> changes (the stack holds implicit knowledge of the offset/order that
>> must now be tracked in the edge cases).
>>
>> Given the stack is 24 bytes, I'm not sure if the extra complexity is
>> worth saving that small amount of memory. Although we would also be
>> getting rid of (3?) functions, so both approaches have pros and cons.
> 
> I consider a simple forward loop over the offset ... less complexity compared to
> a stack structure :)
> 
>>
>> I will implement a patch comparing your solution against mine and send
>> it here, then we can decide which approach is better.
> 
> Right, throw it over the fence and I'll see how to improve it further.

Ok heres what the diff looks like on top of my V19. 

you can access the tree here https://gitlab.com/npache/linux/-/commits/mthp-v19?ref_type=heads for easier review.

So far I have no problem with this approach it appeared cleaner than i thought. Did some light testing. Gonna throw it more through the ringer tomorrow.