linux-kernel - Re: [PATCH RFC] mm: madvise: use walk_page_range_vma() for madvise_free_single

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Message-ID: <CAGsJ_4y3zWS_rHY4=WWuA9BANYwR=r-j9nrfiX2TAQwuo11JdA@mail.gmail.com>
Date: Tue, 3 Jun 2025 20:47:04 +1200
From: Barry Song <21cnbao@...il.com>
To: Dev Jain <dev.jain@....com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Barry Song <v-songbaohua@...o.com>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	David Hildenbrand <david@...hat.com>, Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>, 
	Suren Baghdasaryan <surenb@...gle.com>, Lokesh Gidra <lokeshgidra@...gle.com>, 
	Tangquan Zheng <zhengtangquan@...o.com>
Subject: Re: [PATCH RFC] mm: madvise: use walk_page_range_vma() for madvise_free_single_vma()

On Tue, Jun 3, 2025 at 6:11 PM Dev Jain <dev.jain@....com> wrote:
>
>
> On 03/06/25 7:01 am, Barry Song wrote:
> > From: Barry Song <v-songbaohua@...o.com>
> >
> > We've already found the VMA before calling madvise_free_single_vma(),
> > so calling walk_page_range() and doing find_vma() again seems
> > unnecessary. It also prevents potential optimizations for MADV_FREE
> > to use a per-VMA lock.
> >
> > Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> > Cc: David Hildenbrand <david@...hat.com>
> > Cc: Vlastimil Babka <vbabka@...e.cz>
> > Cc: Jann Horn <jannh@...gle.com>
> > Cc: Suren Baghdasaryan <surenb@...gle.com>
> > Cc: Lokesh Gidra <lokeshgidra@...gle.com>
> > Cc: Tangquan Zheng <zhengtangquan@...o.com>
> > Signed-off-by: Barry Song <v-songbaohua@...o.com>
> > ---
> >   mm/madvise.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index d408ffa404b3..c6a28a2d3ff8 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -826,7 +826,7 @@ static int madvise_free_single_vma(struct madvise_behavior *madv_behavior,
> >
> >       mmu_notifier_invalidate_range_start(&range);
> >       tlb_start_vma(tlb, vma);
> > -     walk_page_range(vma->vm_mm, range.start, range.end,
> > +     walk_page_range_vma(vma, range.start, range.end,
> >                       &madvise_free_walk_ops, tlb);
> >       tlb_end_vma(tlb, vma);
> >       mmu_notifier_invalidate_range_end(&range);
>
> Can similar optimizations be made in madvise_willneed(), madvise_cold_page_range(), etc?

Yes, I think the same code flow applies to madvise_willneed,
madvise_cold_page_range, and similar functions, though my current
interest is more on madvise_free.

Let me prepare a v2 that includes those as well.

>

Thanks
Barry