Yes, I understand now, through google "memory hole" ; thanks a lot.
recent regular machine often have ~1G hole. It is true.
I found from boot msg:
55:<6>[ 0.000000] Memory: 4171008k/5242880k available (4404k kernel code,
788584k absent, 283288k reserved, 7685k data, 1340k init)
it tells me where 1G memory went .
-----原始邮件-----
From: KOSAKI Motohiro
Sent: Wednesday, October 17, 2012 9:43 AM
To: Jun Hu
Cc: linux-mm
Subject: Re: [help] kernel boot parameter "mem=xx" disparity
On Tue, Oct 16, 2012 at 8:55 PM, Jun Hu <duanshuidao@xxxxxxxxxxx> wrote:
Hi Guys:
My machine has 8G memory, when I use kernel boot parameter mem=5G , it
only
display “4084 M” using “free –m “.
where the “5120-4084 = 1036M “ memory run?
mem is misleading parameter. It is not specify amount memoy. It is specify
maximum recognized address. Thus when your machine have some memory
hole, you see such result. Don't worry, recent regular machine often have
~1G hole.
Detailed memory map is logged in /var/log/messages as a part of boot
messages.
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