Re: [PATCH v6 1/5] mm: rmap: support batched checks of the references for large folios

[David Hildenbrand (Arm)]

On 3/10/26 02:37, Baolin Wang wrote:
> 
> 
> On 3/7/26 4:02 PM, Barry Song wrote:
>> On Sat, Mar 7, 2026 at 10:22 AM Baolin Wang
>> <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>>>
>>>
>>>
>>>
>>> Thanks.
>>>
>>>
>>> Yes. In addition, this will involve many architectures’ implementations
>>> and their differing TLB flush mechanisms, so it’s difficult to make a
>>> reasonable per-architecture measurement. If any architecture has a more
>>> efficient flush method, I’d prefer to implement an architecture‑specific
>>> clear_flush_young_ptes().
>>
>> Right! Since TLBI is usually quite expensive, I wonder if a generic
>> implementation for architectures lacking clear_flush_young_ptes()
>> might benefit from something like the below (just a very rough idea):
>>
>> int clear_flush_young_ptes(struct vm_area_struct *vma,
>>                  unsigned long addr, pte_t *ptep, unsigned int nr)
>> {
>>          unsigned long curr_addr = addr;
>>          int young = 0;
>>
>>          while (nr--) {
>>                  young |= ptep_test_and_clear_young(vma, curr_addr,
>> ptep);
>>                  ptep++;
>>                  curr_addr += PAGE_SIZE;
>>          }
>>
>>          if (young)
>>                  flush_tlb_range(vma, addr, curr_addr);
>>          return young;
>> }
> 
> I understand your point. I’m concerned that I can’t test this patch on
> every architecture to validate the benefits. Anyway, let me try this on
> my X86 machine first.

In any case, please make that a follow-up patch :)

-- 
Cheers,

David