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

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Date:   Thu, 9 Jul 2020 12:27:11 +0000
From:   "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
To:     "liwei (CM)" <liwei213@...wei.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: RE: [PATCH] arm64: mm: free unused memmap for sparse memory model
 that define VMEMMAP



> -----Original Message-----
> From: liwei (CM)
> Sent: Wednesday, July 8, 2020 7:52 PM
> To: Song Bao Hua (Barry Song) <song.bao.hua@...ilicon.com>;
> catalin.marinas@....com; will@...nel.org
> Cc: 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>; 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.

At the first glance of this patch, I suspect that this bootmem may be used by hot-added memory.
If you confirm this won't happen, please ignore my noise.

BTW, next time, bear in mind that top-post is not a good way to reply mail :-)

> 
> 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