Re: [PATCH 1/1] mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check

[David Hildenbrand]

On 22.02.24 08:51, Lance Yang wrote:
> Hey,
>
> On an Intel Core i5 CPU, the time taken by
> khugepaged to scan the address space of
> the process, which has been set with the
> MMF_DISABLE_THP flag after being added
> to the mm_slots list, is as follows (shorter is better):
>
> VMA Count |   Old   |   New   |  Change
> ---------------------------------------
>      50     |   23us  |    9us  |  -60.9%
>     100     |   32us  |    9us  |  -71.9%
>     200     |   44us  |    9us  |  -79.5%
>     400     |   75us  |    9us  |  -88.0%
>     800     |   98us  |    9us  |  -90.8%
>
> IIUC, once the count of VMAs for the process
> exceeds page_to_scan, khugepaged needs to
> wait for scan_sleep_millisecs ms before scanning
> the next process. IMO, unnecessary scans could
> actually be skipped with a very inexpensive
> mm->flags check in this case.

FWIW

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb