linux-kernel - Re: [PATCH v1 02/10] mm: pass gfp flags and order to vma_alloc_zeroed_movable

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Message-ID: <CAOUHufYWtsAU4PvKpVhzJUeQb9cd+BifY9KzgceBXHp2F2dDRg@mail.gmail.com>
Date:   Mon, 26 Jun 2023 20:27:04 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Ryan Roberts <ryan.roberts@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yin Fengwei <fengwei.yin@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH v1 02/10] mm: pass gfp flags and order to vma_alloc_zeroed_movable_folio()

On Mon, Jun 26, 2023 at 11:14 AM Ryan Roberts <ryan.roberts@....com> wrote:
>
> Allow allocation of large folios with vma_alloc_zeroed_movable_folio().
> This prepares the ground for large anonymous folios. The generic
> implementation of vma_alloc_zeroed_movable_folio() now uses
> clear_huge_page() to zero the allocated folio since it may now be a
> non-0 order.
>
> Currently the function is always called with order 0 and no extra gfp
> flags, so no functional change intended. But a subsequent commit will
> take advantage of the new parameters to allocate large folios. The extra
> gfp flags will be used to control the reclaim policy.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  arch/alpha/include/asm/page.h   |  5 +++--
>  arch/arm64/include/asm/page.h   |  3 ++-
>  arch/arm64/mm/fault.c           |  7 ++++---
>  arch/ia64/include/asm/page.h    |  5 +++--
>  arch/m68k/include/asm/page_no.h |  7 ++++---
>  arch/s390/include/asm/page.h    |  5 +++--
>  arch/x86/include/asm/page.h     |  5 +++--
>  include/linux/highmem.h         | 23 +++++++++++++----------
>  mm/memory.c                     |  5 +++--
>  9 files changed, 38 insertions(+), 27 deletions(-)
>
> diff --git a/arch/alpha/include/asm/page.h b/arch/alpha/include/asm/page.h
> index 4db1ebc0ed99..6fc7fe91b6cb 100644
> --- a/arch/alpha/include/asm/page.h
> +++ b/arch/alpha/include/asm/page.h
> @@ -17,8 +17,9 @@
>  extern void clear_page(void *page);
>  #define clear_user_page(page, vaddr, pg)       clear_page(page)
>
> -#define vma_alloc_zeroed_movable_folio(vma, vaddr) \
> -       vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, 0, vma, vaddr, false)
> +#define vma_alloc_zeroed_movable_folio(vma, vaddr, gfp, order) \
> +       vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO | (gfp), \
> +                       order, vma, vaddr, false)

I don't think we need to worry about gfp if we want to make a minimum
series. There would be many discussion points around it, e.g., I
already disagree with what you chose: GFP_TRANSHUGE_LIGHT would be
more suitable than __GFP_NORETRY, and there are even better options
than GFP_TRANSHUGE_LIGHT.