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From: Catalin Marinas <catalin.marinas@arm.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Will Deacon <will@kernel.org>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Steve Capper <Steve.Capper@arm.com>
Subject: Re: [PATCH] arm64/mm: Drop THP conditionality from FORCE_MAX_ZONEORDER
Date: Mon, 1 Mar 2021 15:18:00 +0000	[thread overview]
Message-ID: <20210301151759.GC3250@arm.com> (raw)
In-Reply-To: <1614597914-28565-1-git-send-email-anshuman.khandual@arm.com>

On Mon, Mar 01, 2021 at 04:55:14PM +0530, Anshuman Khandual wrote:
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 9cd33c7be429..d4690326274a 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1156,8 +1156,8 @@ config XEN
>  
>  config FORCE_MAX_ZONEORDER
>  	int
> -	default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE)
> -	default "12" if (ARM64_16K_PAGES && TRANSPARENT_HUGEPAGE)
> +	default "14" if ARM64_64K_PAGES
> +	default "12" if ARM64_16K_PAGES
>  	default "11"
>  	help
>  	  The kernel memory allocator divides physically contiguous memory

I think this makes sense. The original "14" was added by Steve C in
commit d03bb1455f3a ("ARM64: mm: Raise MAX_ORDER for 64KB pages and
THP.") back in 3.11. It looks like hugetlbfs (and the HUGETLB_PAGE_ORDER
definition) was added in the same kernel but we somehow missed the
!TRANSPARENT_HUGEPAGE case and smaller page order. The warning in
__fragmentation_index() was added much later in 4.14.

Anyway, the patch looks fine to me, we could apply it to some past
stable kernels:

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

An alternative would have be to add a dependency on both
TRANSPARENT_HUGEPAGE and HUGETLB_PAGE but I'm not sure it's worth it.

-- 
Catalin

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  reply	other threads:[~2021-03-01 15:19 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-01 11:25 [PATCH] arm64/mm: Drop THP conditionality from FORCE_MAX_ZONEORDER Anshuman Khandual
2021-03-01 15:18 ` Catalin Marinas [this message]
2021-03-08 14:40 ` Will Deacon

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