linux-kernel - [QUESTION 1/2] Simple question about pagemap

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Date:	Mon, 29 Jun 2015 20:59:46 +0900
From:	Akira Nakajima <linolenic@...mail.com>
To:	linux-kernel@...r.kernel.org
Subject: [QUESTION 1/2] Simple question about pagemap

Sorry for simple question.

1. Why physical address is greater than the installed memory?

-- Installed memory is 8GB

RHEL7# grep MemTotal /proc/meminfo
MemTotal:        7840900 kB

RHEL7# dmidecode | grep -A 5 'Memory Device' | grep Size
        Size: 4096 MB
        Size: No Module Installed
        Size: 4096 MB
        Size: No Module Installed


-- Physical address is greater than 8GB

RHEL7# wc -c /proc/kpageflags
19136504 /proc/kpageflags

19136504 / 8Bytes x 4KB = 9.125GB


-- My program which is using pagemap shows following.
  ( From left, Phy_addr, Phy_addr(hex), Virtual_addr(hex), process(PID), kpageflags, [kpagecount] )

  9 G  127 M  112 K   247f1c000 v_addr:     7f8bf44b7000 NetworkManager (630)
__RU_lA____M_____________       [56]
  9 G  127 M  116 K   247f1d000 v_addr:     7fa9b3adf000 gdm-session-wor(1964)
__RU_lA____M_____________       [5]
  9 G  127 M  120 K   247f1e000 v_addr:     7f177ce2e000 systemd-journal(514)
__RU_lA____M_____________       [87]


-- crash shows same physical address.

crash> vtop -c 514 7f177ce2e000
VIRTUAL     PHYSICAL
7f177ce2e000  247f1e000



Why greater than installed memory?
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