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

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: liwei (CM)
> Sent: Wednesday, July 8, 2020 7:52 PM
> To: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>;
> catalin.marinas@xxxxxxx; will@xxxxxxxxxx
> Cc: fengbaopeng <fengbaopeng2@xxxxxxxxxxxxx>; nsaenzjulienne@xxxxxxx;
> steve.capper@xxxxxxx; rppt@xxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; sujunfei
> <sujunfei2@xxxxxxxxxxxxx>; Xiaqing (A) <saberlily.xia@xxxxxxxxxxxxx>;
> Yaobaofeng (Yaobaofeng) <yaobaofeng@xxxxxxxxxx>
> 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@xxxxxxxxxx>; catalin.marinas@xxxxxxx;
> will@xxxxxxxxxx
> 抄送: fengbaopeng <fengbaopeng2@xxxxxxxxxxxxx>; nsaenzjulienne@xxxxxxx;
> steve.capper@xxxxxxx; rppt@xxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; sujunfei
> <sujunfei2@xxxxxxxxxxxxx>
> 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@xxxxxxx; will@xxxxxxxxxx
> > Cc: liwei (CM) <liwei213@xxxxxxxxxx>; fengbaopeng
> > <fengbaopeng2@xxxxxxxxxxxxx>; nsaenzjulienne@xxxxxxx;
> > steve.capper@xxxxxxx; rppt@xxxxxxxxxxxxx; Song Bao Hua (Barry Song)
> > <song.bao.hua@xxxxxxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; sujunfei <sujunfei2@xxxxxxxxxxxxx>
> > 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@xxxxxxxxxx>
> > Signed-off-by: Chen Feng <puck.chen@xxxxxxxxxxxxx>
> > Signed-off-by: Xia Qing <saberlily.xia@xxxxxxxxxxxxx>
> > ---
> >  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