On 7/14/2023 11:41 AM, Hugh Dickins wrote: > On Fri, 14 Jul 2023, Yin, Fengwei wrote: >> On 7/14/2023 10:21 AM, Hugh Dickins wrote: >>> On Wed, 12 Jul 2023, Yin Fengwei wrote: >>>> On 7/12/23 14:23, Yu Zhao wrote: >>>>> On Wed, Jul 12, 2023 at 12:02 AM Yin Fengwei <fengwei.yin@xxxxxxxxx> wrote: >>>>>> --- a/ >>>>>> +++ b/mm/internal.h >>>>>> @@ -643,7 +643,8 @@ static inline void mlock_vma_folio(struct folio *folio, >>>>>> * still be set while VM_SPECIAL bits are added: so ignore it then. >>>>>> */ >>>>>> if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED) && >>>>>> - (compound || !folio_test_large(folio))) >>>>>> + (compound || !folio_test_large(folio) || >>>>>> + folio_in_range(folio, vma, vma->vm_start, vma->vm_end))) >>>>>> mlock_folio(folio); >>>>>> } >>>>> >>>>> This can be simplified: >>>>> 1. remove the compound parameter >>>> Yes. There is not difference here for pmd mapping of THPs and pte mappings of THPs >>>> if the only condition need check is whether the folio is within VMA range or not. >>>> >>>> But let me add Huge for confirmation. >>> >>> I'm not sure what it is that you need me to confirm: if the folio fits >>> within the vma, then the folio fits within the vma, pmd-mapped or not. >> Sorry. My bad. I should speak it out for what I want your confirmation: >> Whether we can remove the compound and use whether folio is within >> VMA instead. >> >> I suppose you answer is Yes. > > Yes (if it all works out going that way). > >> >>> >>> (And I agree with Yu that it's better to drop the folio_test_large() >>> check too.) >> My argument was folio_test_large() can filter the normal 4K page out so >> it doesn't need to call folio_in_range() which looks to me a little bit >> heavy for normal 4K page. And the deal was move folio_test_large() >> to folio_in_range() like function so simplify the code in caller side. > > I realized that, but agree with Yu. OK. I will rethink this as both Yu and you suggested same thing. > > It looked a little over-engineered to me, but I didn't spend long enough > looking to understand why there's folio_within_vma() distinct from > folio_in_range(), when everyone(?) calls folio_in_range() with the same > arguments vma->vm_start, vma->vm_end. madvise could call folio_in_range() with start/end from user space instead of using VMA range. Regards Yin, Fengwei > >> >>> >>> This idea, of counting the folio as mlocked according to whether the >>> whole folio fits within the vma, does seem a good idea to me: worth >>> pursuing. But whether the implementation adds up and works out, I >>> have not checked. It was always difficult to arrive at a satisfactory >>> compromise in mlocking compound pages: I hope this way does work out. >> This is the purpose of this patch. :). Thanks. >> >> >> Regards >> Yin, Fengwei >> >>> >>> Hugh
