Dear all,
My embedded linux device has 16MB of RAM. I tried to allocate 8MB of memory by using a small program "malloc_test". After that, I computed how much free memory is left in my system. My calculation gives me 4140K but the /proc/meminfo shows only 256K free. Can someone please help me to figure out whether my calculation is wrong or the /proc/meminfo is wrong or the /proc/$PID/stat where "ps" gets its VmSize(VmRss) data is wrong ?
Thanks a lot...
Code:
$$$ =======================================================
$$$ Original memory information after booting up
$$$ =======================================================
wlan[0,0]-> cat /proc/iomem
00000000-00ffffff : System RAM
00041000-001cbe97 : Kernel code
001e4000-001fbfff : Kernel data
$$$ =======================================================
$$$ Kernel size: 1617559(1580K code) + 98303(96K data) = 1676K
$$$ =======================================================
wlan[0,0]-> lsmod
Module Size Used by Tainted: P
ath_ahb 67376 1
wlan_xauth 332 0 (unused)
wlan_wep 4092 0 (unused)
wlan_tkip 10492 0 (unused)
wlan_ccmp 5820 0 (unused)
wlan_acl 2572 1
ath_dfs 26880 0 [ath_ahb]
ath_rate_atheros 25976 0 [ath_ahb]
ath_hal 185520 1 [ath_ahb ath_rate_atheros]
wlan_scan_sta 8444 0 (unused)
wlan_scan_ap 2508 0 (unused)
wlan 146448 1 [ath_ahb wlan_xauth wlan_wep wlan_tkip wlan_ccmp wlan_acl ath_rate_atheros wlan_scan_sta wlan_scan_ap]
$$$ =======================================================
$$$ Kernel modules size: 486460 = 475K
$$$ =======================================================
wlan[0,0]-> ps
PID Uid VmSize Stat Command
1 root 412 S init
2 root SW [keventd]
3 root RWN [ksoftirqd_CPU0]
4 root SW [kswapd]
5 root SW [bdflush]
6 root SW [kupdated]
8 root SW [mtdblockd]
18 root 420 S logger -s -p 6 -t
20 root 600 S /bin/ash --login
22 root 372 S klogd
50 root SWN [jffs2_gcd_mtd2]
88 root 276 D ifconfig eth0 up
333 root 276 D ifconfig eth0 up
1984 root 468 S udhcpc -t 0 -i eth0 -H AcctonAP -b -p /var/run/eth0.p
2180 root 408 S /sbin/syslogd -C16 -m 0
2583 root 384 S crond -c /etc/crontabs
2641 root 420 S httpd -p 80 -h /www -r AcctonAP
2834 root 348 S telnetd -l /bin/login
2840 root 308 S /sbin/watchdog /dev/misc/watchdog
2841 root 300 D /sbin/watchdog /dev/misc/watchdog
3081 nobody 416 S dnsmasq -F 192.168.1.100,192.168.1.149,255.255.255.0,
3194 root 400 S /usr/sbin/dropbear -p 22
5188 root 388 R ps
$$$ =======================================================
$$$ Process VmRSS memory usage: 5612K
$$$ only count 1 instance of: ifconfig and watchdog
$$$ =======================================================
wlan[0,0]-> cat /proc/meminfo
total: used: free: shared: buffers: cached:
Mem: 14307328 9793536 4513792 0 1064960 3198976
Swap: 0 0 0
MemTotal: 13972 kB
MemFree: 4408 kB
MemShared: 0 kB
Buffers: 1040 kB
Cached: 3124 kB
SwapCached: 0 kB
Active: 2880 kB
Inactive: 1328 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 13972 kB
LowFree: 4408 kB
SwapTotal: 0 kB
SwapFree: 0 kB
$$$ =======================================================
$$$ Total memory: 13972K
$$$ Total Process VmRSS: 5612K
$$$ Page Cache: 3124K
$$$ Buffer Cache: 1040K
$$$ ==============================
$$$ Free: 4196K seems correct...
$$$ =======================================================
wlan[0,0]-> free
total used free shared buffers
Mem: 13972 9472 4500 0 1040
Swap: 0 0 0
Total: 13972 9472 4500
$$$ =======================================================
$$$ Now, try to malloc 8 mega bytes of memory
$$$ =======================================================
wlan[0,0]-> ./malloc_test 8 &
malloc success 0-th mega at 0x2ABE1008
malloc success 1-th mega at 0x2ACE2008
malloc success 2-th mega at 0x2ADE3008
malloc success 3-th mega at 0x2AEE4008
malloc success 4-th mega at 0x2AFE5008
malloc success 5-th mega at 0x2B0E6008
malloc success 6-th mega at 0x2B1E7008
malloc success 7-th mega at 0x2B2E8008
$$$ =======================================================
$$$ The system responses extremely slow now....
$$$ =======================================================
wlan[0,0]-> ps
PID Uid VmSize Stat Command
1 root 72 S init
2 root SW [keventd]
3 root SWN [ksoftirqd_CPU0]
4 root SW [kswapd]
5 root SW [bdflush]
6 root SW [kupdated]
8 root SW [mtdblockd]
18 root 80 S logger -s -p 6 -t
20 root 152 S /bin/ash --login
22 root 60 S klogd
50 root SWN [jffs2_gcd_mtd2]
88 root 44 D ifconfig eth0 up
272 root 44 D ifconfig eth0 up
1638 root 96 S udhcpc -t 0 -i eth0 -H AcctonAP -b -p /var/run/eth0.p
2049 root 72 S /sbin/syslogd -C16 -m 0
2532 root 60 S crond -c /etc/crontabs
2541 root 60 S /usr/sbin/dropbear -p 22
2592 root 84 S httpd -p 80 -h /www -r AcctonAP
2785 root 64 S telnetd -l /bin/login
2791 root 56 S /sbin/watchdog /dev/misc/watchdog
2792 root 56 D /sbin/watchdog /dev/misc/watchdog
3027 nobody 64 S dnsmasq -F 192.168.1.100,192.168.1.149,255.255.255.0,
3824 root 8260 S ./malloc_test 8
3826 root 144 R ps
$$$ =======================================================
$$$ Process VmRSS memory usage: 9368K
$$$ only count 1 instance of: ifconfig and watchdog
$$$ =======================================================
wlan[0,0]-> cat /proc/meminfo
total: used: free: shared: buffers: cached:
Mem: 14307328 14045184 262144 0 143360 331776
Swap: 0 0 0
MemTotal: 13972 kB
MemFree: 256 kB
MemShared: 0 kB
Buffers: 140 kB
Cached: 324 kB
SwapCached: 0 kB
Active: 200 kB
Inactive: 312 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 13972 kB
LowFree: 256 kB
SwapTotal: 0 kB
SwapFree: 0 kB
$$$ =======================================================
$$$ Free memory computation:
$$$ =======================================================
$$$ Total memory: 13972K
$$$ Total Process VmRSS: 9368K
$$$ Page Cache: 324K
$$$ Buffer Cache: 140K
$$$ ==============================
$$$ Free: 4140K differs by 3900K???
$$$ =======================================================
wlan[0,0]-> free
total used free shared buffers
Mem: 13972 13692 280 0 104
Swap: 0 0 0
Total: 13972 13692 280
