linux-kernel - Re: [PATCH v4 6/6] memblock: Disable mirror feature if kernelcore is not specified

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Message-ID: <590a1211-d316-d51d-6577-eb9983126dd0@huawei.com>
Date:   Mon, 13 Jun 2022 17:13:02 +0800
From:   mawupeng <mawupeng1@...wei.com>
To:     <corbet@....net>, <will@...nel.org>, <ardb@...nel.org>,
        <catalin.marinas@....com>
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        <mawupeng1@...wei.com>
Subject: Re: [PATCH v4 6/6] memblock: Disable mirror feature if kernelcore is
 not specified



On 6/13/2022 4:21 PM, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@...wei.com>
> 
> If system have some mirrored memory and mirrored feature is not specified
> in boot parameter, the basic mirrored feature will be enabled and this will
> lead to the following situations:
> 
> - memblock memory allocation prefers mirrored region. This may have some
>   unexpected influence on numa affinity.
> 
> - contiguous memory will be split into several parts if parts of them
>   is mirrored memory via memblock_mark_mirror().
> 
> To fix this, variable mirrored_kernelcore will be checked in
> memblock_mark_mirror(). Mark mirrored memory with flag MEMBLOCK_MIRROR iff
> kernelcore=mirror is added in the kernel parameters.
> 
> Signed-off-by: Ma Wupeng <mawupeng1@...wei.com>
> ---
>  mm/internal.h   | 2 ++
>  mm/memblock.c   | 3 +++
>  mm/page_alloc.c | 2 +-
>  3 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index c0f8fbe0445b..ddd2d6a46f1b 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -861,4 +861,6 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
>  
>  DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
>  
> +extern bool mirrored_kernelcore;
> +
>  #endif	/* __MM_INTERNAL_H */
> diff --git a/mm/memblock.c b/mm/memblock.c
> index b1d2a0009733..a9f18b988b7f 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -924,6 +924,9 @@ int __init_memblock memblock_clear_hotplug(phys_addr_t base, phys_addr_t size)
>   */
>  int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
>  {
> +	if (!mirrored_kernelcore)
> +		return 0;
> +
>  	system_has_some_mirror = true;
>  
>  	return memblock_setclr_flag(base, size, 1, MEMBLOCK_MIRROR);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e008a3df0485..9b030aeb4983 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -356,7 +356,7 @@ static unsigned long required_kernelcore_percent __initdata;
>  static unsigned long required_movablecore __initdata;
>  static unsigned long required_movablecore_percent __initdata;
>  static unsigned long zone_movable_pfn[MAX_NUMNODES] __initdata;
> -static bool mirrored_kernelcore __meminitdata;
> +bool mirrored_kernelcore __initdata;

__initdata here is not suitable and will lead to compile warnings.

In my test, __initdata_memblock and ro_after_init are both fine, but I am not
sure which one to choose? Do you have any idea on this?

>  
>  /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
>  int movable_zone;