linux-kernel - Re: [PATCH v2 1/2] mm/hugetlb: Cleanup ARCH_HAS_GIGANTIC

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Date:   Tue, 16 May 2017 15:52:46 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        akpm@...ux-foundation.org, mpe@...erman.id.au,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 1/2] mm/hugetlb: Cleanup ARCH_HAS_GIGANTIC_PAGE

On 05/16/2017 02:47 PM, Aneesh Kumar K.V wrote:
> This moves the #ifdef in C code to a Kconfig dependency. Also we move the
> gigantic_page_supported() function to be arch specific. This gives arch to
> conditionally enable runtime allocation of gigantic huge page. Architectures
> like ppc64 supports different gigantic huge page size (16G and 1G) based on the
> translation mode selected. This provides an opportunity for ppc64 to enable
> runtime allocation only w.r.t 1G hugepage.

Right.

> 
> No functional change in this patch.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  arch/arm64/Kconfig               | 2 +-
>  arch/arm64/include/asm/hugetlb.h | 4 ++++
>  arch/s390/Kconfig                | 2 +-
>  arch/s390/include/asm/hugetlb.h  | 3 +++
>  arch/x86/Kconfig                 | 2 +-
>  mm/hugetlb.c                     | 7 ++-----
>  6 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 3741859765cf..1f8c1f73aada 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -11,7 +11,7 @@ config ARM64
>  	select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
>  	select ARCH_HAS_ELF_RANDOMIZE
>  	select ARCH_HAS_GCOV_PROFILE_ALL
> -	select ARCH_HAS_GIGANTIC_PAGE
> +	select ARCH_HAS_GIGANTIC_PAGE if MEMORY_ISOLATION && COMPACTION && CMA
>  	select ARCH_HAS_KCOV
>  	select ARCH_HAS_SET_MEMORY
>  	select ARCH_HAS_SG_CHAIN
> diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
> index bbc1e35aa601..793bd73b0d07 100644
> --- a/arch/arm64/include/asm/hugetlb.h
> +++ b/arch/arm64/include/asm/hugetlb.h
> @@ -83,4 +83,8 @@ extern void huge_ptep_set_wrprotect(struct mm_struct *mm,
>  extern void huge_ptep_clear_flush(struct vm_area_struct *vma,
>  				  unsigned long addr, pte_t *ptep);
>  
> +#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
> +static inline bool gigantic_page_supported(void) { return true; }
> +#endif
> +
>  #endif /* __ASM_HUGETLB_H */
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index a2dcef0aacc7..a41bbf420dda 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -67,7 +67,7 @@ config S390
>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
>  	select ARCH_HAS_ELF_RANDOMIZE
>  	select ARCH_HAS_GCOV_PROFILE_ALL
> -	select ARCH_HAS_GIGANTIC_PAGE
> +	select ARCH_HAS_GIGANTIC_PAGE if MEMORY_ISOLATION && COMPACTION && CMA
>  	select ARCH_HAS_KCOV
>  	select ARCH_HAS_SET_MEMORY
>  	select ARCH_HAS_SG_CHAIN
> diff --git a/arch/s390/include/asm/hugetlb.h b/arch/s390/include/asm/hugetlb.h
> index cd546a245c68..89057b2cc8fe 100644
> --- a/arch/s390/include/asm/hugetlb.h
> +++ b/arch/s390/include/asm/hugetlb.h
> @@ -112,4 +112,7 @@ static inline pte_t huge_pte_modify(pte_t pte, pgprot_t newprot)
>  	return pte_modify(pte, newprot);
>  }
>  
> +#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
> +static inline bool gigantic_page_supported(void) { return true; }
> +#endif
>  #endif /* _ASM_S390_HUGETLB_H */
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index cc98d5a294ee..30a6328136ac 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -22,7 +22,7 @@ config X86_64
>  	def_bool y
>  	depends on 64BIT
>  	# Options that are inherently 64-bit kernel only:
> -	select ARCH_HAS_GIGANTIC_PAGE
> +	select ARCH_HAS_GIGANTIC_PAGE if MEMORY_ISOLATION && COMPACTION && CMA
>  	select ARCH_SUPPORTS_INT128
>  	select ARCH_USE_CMPXCHG_LOCKREF
>  	select HAVE_ARCH_SOFT_DIRTY

Should not we define gigantic_page_supported() function for X86 as well
like the other two archs above ?