linux-kernel - Re: [PATCH 1/2] mm: mmap: no need to call khugepaged_enter

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Date: Tue, 16 Jan 2024 13:39:20 -0800
From: Yang Shi <shy828301@...il.com>
To: "Huang, Ying" <ying.huang@...el.com>
Cc: oliver.sang@...el.com, riel@...riel.com, fengwei.yin@...el.com, 
	willy@...radead.org, cl@...ux.com, akpm@...ux-foundation.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] mm: mmap: no need to call khugepaged_enter_vma() for stack

On Sun, Jan 14, 2024 at 9:52 PM Huang, Ying <ying.huang@...el.com> wrote:
>
> Yang Shi <shy828301@...il.com> writes:
>
> > From: Yang Shi <yang@...amperecomputing.com>
> >
> > We avoid allocating THP for temporary stack, even tnough
>                                                     ~~~~~~
>                                                     though?

Yeah, it is a typo. Thanks for noticing this.

>
> --
> Best Regards,
> Huang, Ying
>
> > khugepaged_enter_vma() is called for stack VMAs, it actualy returns
> > false.  So no need to call it in the first place at all.
> >
> > Signed-off-by: Yang Shi <yang@...amperecomputing.com>
> > ---
> >  mm/mmap.c | 2 --
> >  1 file changed, 2 deletions(-)
> >
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index b78e83d351d2..2ff79b1d1564 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -2046,7 +2046,6 @@ static int expand_upwards(struct vm_area_struct *vma, unsigned long address)
> >               }
> >       }
> >       anon_vma_unlock_write(vma->anon_vma);
> > -     khugepaged_enter_vma(vma, vma->vm_flags);
> >       mas_destroy(&mas);
> >       validate_mm(mm);
> >       return error;
> > @@ -2140,7 +2139,6 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address)
> >               }
> >       }
> >       anon_vma_unlock_write(vma->anon_vma);
> > -     khugepaged_enter_vma(vma, vma->vm_flags);
> >       mas_destroy(&mas);
> >       validate_mm(mm);
> >       return error;