linux-kernel - 答复: [PATCH] arm64: mm: free unused memmap for sparse memory model that define VMEMMAP

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Date:   Wed, 8 Jul 2020 07:51:54 +0000
From:   "liwei (CM)" <liwei213@...wei.com>
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>
CC:     fengbaopeng <fengbaopeng2@...ilicon.com>,
        "nsaenzjulienne@...e.de" <nsaenzjulienne@...e.de>,
        "steve.capper@....com" <steve.capper@....com>,
        "rppt@...ux.ibm.com" <rppt@...ux.ibm.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        sujunfei <sujunfei2@...ilicon.com>,
        "Xiaqing (A)" <saberlily.xia@...ilicon.com>,
        "Yaobaofeng (Yaobaofeng)" <yaobaofeng@...wei.com>
Subject: 答复: [PATCH] arm64: mm: free unused memmap for sparse memory model that define VMEMMAP

Hi, baohua

Thank you for your attention.

In my understanding of the MEMORY_HOTPLUG this patch has no effect on it. The reason is that in sparse_add_one_section() the memory that memmap needs from Slab if kernel start completed，this memory has nothing to do with memblock alloc/ free memory in the process of kernel start.

You may have a look vmemmap_alloc_block () this function.

If I don't understand right welcome pointed out in a timely manner.

Thanks!


-----邮件原件-----
发件人: Song Bao Hua (Barry Song) 
发送时间: 2020年7月8日 15:19
收件人: liwei (CM) <liwei213@...wei.com>; catalin.marinas@....com; will@...nel.org
抄送: fengbaopeng <fengbaopeng2@...ilicon.com>; nsaenzjulienne@...e.de; steve.capper@....com; rppt@...ux.ibm.com; linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; sujunfei <sujunfei2@...ilicon.com>
主题: RE: [PATCH] arm64: mm: free unused memmap for sparse memory model that define VMEMMAP



> -----Original Message-----
> From: liwei (CM)
> Sent: Wednesday, July 8, 2020 1:56 PM
> To: catalin.marinas@....com; will@...nel.org
> Cc: liwei (CM) <liwei213@...wei.com>; fengbaopeng 
> <fengbaopeng2@...ilicon.com>; nsaenzjulienne@...e.de; 
> steve.capper@....com; rppt@...ux.ibm.com; Song Bao Hua (Barry Song) 
> <song.bao.hua@...ilicon.com>; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; sujunfei <sujunfei2@...ilicon.com>
> Subject: [PATCH] arm64: mm: free unused memmap for sparse memory model 
> that define VMEMMAP
> 
> For the memory hole, sparse memory model that define SPARSEMEM_VMEMMAP 
> do not free the reserved memory for the page map, this patch do it.

Hello Wei,
Just curious if this patch breaks MEMORY_HOTPLUG?

> 
> Signed-off-by: Wei Li <liwei213@...wei.com>
> Signed-off-by: Chen Feng <puck.chen@...ilicon.com>
> Signed-off-by: Xia Qing <saberlily.xia@...ilicon.com>
> ---
>  arch/arm64/mm/init.c | 81
> +++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 71 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 
> 1e93cfc7c47a..d1b56b47d5ba 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -441,7 +441,48 @@ void __init bootmem_init(void)
>  	memblock_dump_all();
>  }
> 

Thanks
Barry