Re: [PATCH v16 6/6] arm64, mm, numa: Add NUMA balancing support for arm64.

[Steve Capper]

On Fri, Apr 08, 2016 at 03:50:28PM -0700, David Daney wrote:
> From: Ganapatrao Kulkarni <gkulkarni@xxxxxxxxxxxxxxxxxx>
> 
> Enable NUMA balancing for arm64 platforms.
> Add pte, pmd protnone helpers for use by automatic NUMA balancing.
> 
> Reviewed-by: Robert Richter <rrichter@xxxxxxxxxx>
> Signed-off-by: Ganapatrao Kulkarni <gkulkarni@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> ---
>  arch/arm64/Kconfig               |  1 +
>  arch/arm64/include/asm/pgtable.h | 15 +++++++++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 99f9b55..a578080 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -11,6 +11,7 @@ config ARM64
>  	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_USE_CMPXCHG_LOCKREF
>  	select ARCH_SUPPORTS_ATOMIC_RMW
> +	select ARCH_SUPPORTS_NUMA_BALANCING
>  	select ARCH_WANT_OPTIONAL_GPIOLIB
>  	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
>  	select ARCH_WANT_FRAME_POINTERS
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 989fef1..89b8f20 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -272,6 +272,21 @@ static inline pgprot_t mk_sect_prot(pgprot_t prot)
>  	return __pgprot(pgprot_val(prot) & ~PTE_TABLE_BIT);
>  }
>  
> +#ifdef CONFIG_NUMA_BALANCING
> +/*
> + * See the comment in include/asm-generic/pgtable.h
> + */
> +static inline int pte_protnone(pte_t pte)
> +{
> +	return (pte_val(pte) & (PTE_VALID | PTE_PROT_NONE)) == PTE_PROT_NONE;
> +}
> +
> +static inline int pmd_protnone(pmd_t pmd)
> +{
> +	return pte_protnone(pmd_pte(pmd));
> +}
> +#endif
> +

Okay, this looks good to me. If we have a PROT_NONE VMA then this is
caught before going into do_numa_page or do_huge_pmd_numa_page (and
there is a BUG_ON inside these functions to catch stragglers.

I've given this a quick test with a PROT_NONE THP and everything worked
as expected (i.e. NUMA didn't trip up).

Reviewed-by: Steve Capper <steve.capper@xxxxxxx>

>  /*
>   * THP definitions.
>   */
> -- 
> 1.8.3.1
> 
> 
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