Re: [PATCH v2 1/4] mm: avoid unnecessary lru drain for wp_can_reuse_anon_folio()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 6/30/26 01:16, Barry Song wrote:
> On Mon, Jun 29, 2026 at 3:52 PM David Hildenbrand (Arm)
> <david@kernel.org> wrote:
> [...]
>>
>> So yeah, if Nadav's reproducer works even without the drain (which I assume), we
>> could indeed think about just removing this optimization here.
> 
> Yet I think the problem is resolved with the exclusive flag.
> Right now, we can still have cases where "exclusive" cannot
> address it, such as:
> 
> #include <sys/mman.h>
> 
> int main(int argc, char *argv[])
> {
>     int i;
>     #define SIZE 30*1024*1024
>     while(1) {
>         volatile int *p = mmap(0, SIZE, PROT_READ | PROT_WRITE,
>              MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>         volatile int q;
> 
>         for (int i = 0; i < SIZE/sizeof(int); i++)
>               p[i] =  i;
>         madvise((void *)p, SIZE, MADV_PAGEOUT);
>         if (!fork())
>              _exit(0);
>         for (int i = 0; i < SIZE/sizeof(int); i++)
>               q = p[i];
>         for (int i = 0; i < SIZE/sizeof(int); i++)
>               p[i] =  i;
>         munmap(p, SIZE);
>     }
>     return 0;
> }
> 
> I assume this is less frequent and less of a concern?

It's unlikely to matter in practice I guess.

-- 
Cheers,

David