linux-kernel - Re: [PATCH] mm: make falutaround selectable

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Message-ID: <42adbf38-7b1a-3039-c309-3d7023fc7c6c@redhat.com>
Date:   Tue, 20 Jul 2021 14:11:52 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Chanho Min <chanho.min@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Gunho Lee <gunho.lee@....com>, Juneho Choi <juno.choi@....com>,
        Inkyu Hwang <inkyu.hwang@....com>
Subject: Re: [PATCH] mm: make falutaround selectable

s/falutaround/faultaround/


On 19.07.21 03:08, Chanho Min wrote:
> While faultaround can have performance gains, on certain platform it
> increases pss and causes swap to occur more frequently. This patch allows
> to unselect faultaround on platforms that do not want this behavior.
> 
> Signed-off-by: Chanho Min <chanho.min@....com>
> ---
>   mm/Kconfig  | 6 ++++++
>   mm/memory.c | 4 ++++
>   2 files changed, 10 insertions(+)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 39a6a977537d..8f834386e7f3 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -750,4 +750,10 @@ config ARCH_HAS_PTE_SPECIAL
>   config ARCH_HAS_HUGEPD
>   	bool
>   
> +config FAULT_AROUND
> +	bool "Enable fault around"
> +	default y
> +	help
> +	 This option enables fault around. If say N, fault_around_bytes set to PAGE_SIZE
> +	 and disables fault around.
>   endmenu
> diff --git a/mm/memory.c b/mm/memory.c
> index 10d2e4734e82..0bb037265dda 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3500,7 +3500,11 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
>   }
>   
>   static unsigned long fault_around_bytes __read_mostly =
> +#ifdef CONFIG_FAULT_AROUND
>   	rounddown_pow_of_two(65536);
> +#else
> +	PAGE_SIZE;
> +#endif
>   
>   #ifdef CONFIG_DEBUG_FS
>   static int fault_around_bytes_get(void *data, u64 *val)
> 


-- 
Thanks,

David / dhildenb