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

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Message-ID: <20160822080101.GE13596@dhcp22.suse.cz>
Date:   Mon, 22 Aug 2016 10:01:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Xie Yisheng <xieyisheng1@...wei.com>
Cc:     akpm@...ux-foundation.org, guohanjun@...wei.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        will.deacon@....com, dave.hansen@...el.com, sudeep.holla@....com,
        catalin.marinas@....com, mark.rutland@....com, robh+dt@...nel.org,
        linux-arm-kernel@...ts.infradead.org, mike.kravetz@...cle.com,
        n-horiguchi@...jp.nec.com
Subject: Re: [RFC PATCH v2 1/2] mm/hugetlb: Introduce ARCH_HAS_GIGANTIC_PAGE

On Mon 22-08-16 10:56:42, Xie Yisheng wrote:
> Avoid making ifdef get pretty unwieldy if many ARCHs support gigantic page.
> No functional change with this patch.
> 
> Signed-off-by: Xie Yisheng <xieyisheng1@...wei.com>
> ---
>  arch/s390/Kconfig | 1 +
>  arch/x86/Kconfig  | 1 +
>  fs/Kconfig        | 4 ++++
>  mm/hugetlb.c      | 2 +-
>  4 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index e751fe2..a8c8fa3 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -72,6 +72,7 @@ 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_KCOV
>  	select ARCH_HAS_SG_CHAIN
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index c580d8c..5cf959c 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -29,6 +29,7 @@ config X86
>  	select ARCH_HAS_ELF_RANDOMIZE
>  	select ARCH_HAS_FAST_MULTIPLIER
>  	select ARCH_HAS_GCOV_PROFILE_ALL
> +	select ARCH_HAS_GIGANTIC_PAGE		if X86_64
>  	select ARCH_HAS_KCOV			if X86_64
>  	select ARCH_HAS_PMEM_API		if X86_64
>  	select ARCH_HAS_MMIO_FLUSH

good

> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b77ad0f 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -199,6 +199,10 @@ config HUGETLBFS
>  config HUGETLB_PAGE
>  	def_bool HUGETLBFS
>  
> +config ARCH_HAS_GIGANTIC_PAGE
> +	depends on HUGETLB_PAGE
> +	bool
> +

but is this really necessary? The code where we use
ARCH_HAS_GIGANTIC_PAGE already depends on HUGETLB_PAGE.

Other than that looks good to me and a nice simplification.

>  source "fs/configfs/Kconfig"
>  source "fs/efivarfs/Kconfig"
>  
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 87e11d8..8488dcc 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1022,7 +1022,7 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
>  		((node = hstate_next_node_to_free(hs, mask)) || 1);	\
>  		nr_nodes--)
>  
> -#if (defined(CONFIG_X86_64) || defined(CONFIG_S390)) && \
> +#if defined(CONFIG_ARCH_HAS_GIGANTIC_PAGE) && \
>  	((defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || \
>  	defined(CONFIG_CMA))
>  static void destroy_compound_gigantic_page(struct page *page,
> -- 
> 1.7.12.4

-- 
Michal Hocko
SUSE Labs