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

On 3/10/26 02:37, Baolin Wang wrote:

On 3/7/26 4:02 PM, Barry Song wrote:

quoted

On Sat, Mar 7, 2026 at 10:22 AM Baolin Wang
[off-list ref] wrote:

quoted

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