Re: [PATCH v2] mm: ksm: Consider the number of ksm_mm_slot in the general_profit calculation

[Chengming Zhou <chengming.zhou@linux.dev>]

On 2024/6/21 03:38, David Hildenbrand wrote:
> On 20.06.24 06:39, Sung-hun Kim wrote:
>> The current version of KSM does not take into account the number of
>> used ksm_mm_slot. Therefore, when users want to obtain profits of
>> KSM, KSM omits the memory used for allocating ksm_mm_slots.
>>
>> This patch introduces a new variable to keep track of the number of
>> allocated ksm_mm_slots. By doing so, KSM will be able to provide a
>> more accurate number of the gains made.
> 
> If you take a look at the calculation explained in 
> Documentation/admin-guide/mm/ksm.rst, we only care about rmap_items, 
> which can grow rather substantially in size.
> 
> We also don't consider other metadata, such as the size of the stable 
> nodes etc. So why should the ksm_mm_slots matter that much that we 
> should track them and account them?

BTW, the size of stable_nodes should be more than these mm_slots,
we have one stable_nodes for each KSM page now.

But agree, we only care about the rmap_items, which is the majority
of used memory resource in KSM.