linux-kernel - Re: [PATCH v1 09/10] arm64: mm: Declare support for large anonymous folios

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Message-ID: <CAOUHufaUT3UzGj-ohPN72CHtgXQHpKFrvJgcPfkJ6HAO=ywKQQ@mail.gmail.com>
Date:   Mon, 26 Jun 2023 20:53:09 -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 09/10] arm64: mm: Declare support for large anonymous folios

On Mon, Jun 26, 2023 at 11:15 AM Ryan Roberts <ryan.roberts@....com> wrote:
>
> For the unhinted case, when THP is not permitted for the vma, don't
> allow anything bigger than 64K. This means we don't waste too much
> memory. Additionally, for 4K pages this is the contpte size, and for
> 16K, this is (usually) the HPA size when the uarch feature is
> implemented. For the hinted case, when THP is permitted for the vma,
> allow the contpte size for all page size configurations; 64K for 4K, 2M
> for 16K and 2M for 64K.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  arch/arm64/Kconfig | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 343e1e1cae10..0e91b5bc8cd9 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -243,6 +243,7 @@ config ARM64
>         select TRACE_IRQFLAGS_SUPPORT
>         select TRACE_IRQFLAGS_NMI_SUPPORT
>         select HAVE_SOFTIRQ_ON_OWN_STACK
> +       select ARCH_SUPPORTS_LARGE_ANON_FOLIO
>         help
>           ARM 64-bit (AArch64) Linux support.
>
> @@ -281,6 +282,18 @@ config ARM64_CONT_PMD_SHIFT
>         default 5 if ARM64_16K_PAGES
>         default 4
>
> +config ARCH_LARGE_ANON_FOLIO_NOTHP_ORDER_MAX
> +       int
> +       default 0 if ARM64_64K_PAGES    # 64K (1 page)
> +       default 2 if ARM64_16K_PAGES    # 64K (4 pages; benefits from HPA where HW supports it)
> +       default 4 if ARM64_4K_PAGES     # 64K (16 pages; eligible for contpte-mapping)
> +
> +config ARCH_LARGE_ANON_FOLIO_THP_ORDER_MAX
> +       int
> +       default 5 if ARM64_64K_PAGES    # 2M  (32 page; eligible for contpte-mapping)
> +       default 7 if ARM64_16K_PAGES    # 2M  (128 pages; eligible for contpte-mapping)
> +       default 4 if ARM64_4K_PAGES     # 64K (16 pages; eligible for contpte-mapping)
> +
>  config ARCH_MMAP_RND_BITS_MIN
>         default 14 if ARM64_64K_PAGES
>         default 16 if ARM64_16K_PAGES

Can we please just add one Kconfig for the large anon folio feature,
i.e., ARCH_WANTS_PTE_ORDER, for now?

Feel free to add as many as you wish for arm specific features like
HPA and contpte.