server memory consumption

Hi people!

So, I having trouble with my vps. Lots of OOM and I simply don't know what is eating my ram.

Some info:

# cat /etc/redhat-release CentOS Linux release 7.2.1511 (Core) 

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# uname -a Linux hostname 3.10.0-327.13.1.el7.x86_64 #1 SMP Thu Mar 31 16:04:38 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux 

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# free -mh total used free shared buff/cache available Mem: 489M 367M 41M 976K 80M 85M 

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# grep Slab /proc/meminfo Slab: 41064 kB 

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# ps_mem Private + Shared = RAM used Program 4.0 KiB + 12.5 KiB = 16.5 KiB agetty 4.0 KiB + 41.5 KiB = 45.5 KiB systemd-udevd 4.0 KiB + 51.5 KiB = 55.5 KiB wpa_supplicant 4.0 KiB + 53.0 KiB = 57.0 KiB lvmetad 88.0 KiB + 52.0 KiB = 140.0 KiB 3proxy 116.0 KiB + 39.0 KiB = 155.0 KiB crond 188.0 KiB + 27.0 KiB = 215.0 KiB dnsmasq 196.0 KiB + 60.0 KiB = 256.0 KiB auditd 4.0 KiB + 283.5 KiB = 287.5 KiB mpd 412.0 KiB + 202.0 KiB = 614.0 KiB fail2ban-server 552.0 KiB + 71.5 KiB = 623.5 KiB systemd-logind 576.0 KiB + 97.0 KiB = 673.0 KiB systemd-journald 548.0 KiB + 129.0 KiB = 677.0 KiB rsyslogd 636.0 KiB + 54.0 KiB = 690.0 KiB dbus-daemon 488.0 KiB + 242.5 KiB = 730.5 KiB tuned 444.0 KiB + 307.0 KiB = 751.0 KiB polkitd 1.1 MiB + 353.5 KiB = 1.4 MiB NetworkManager 1.1 MiB + 607.0 KiB = 1.7 MiB sudo 1.0 MiB + 1.1 MiB = 2.1 MiB bash (2) 1.5 MiB + 2.7 MiB = 4.2 MiB sshd (3) 5.5 MiB + 120.5 KiB = 5.6 MiB systemd --------------------------------- 20.8 MiB ================================= 

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# df -ht tmpfs Filesystem Size Used Avail Use% Mounted on tmpfs 245M 0 245M 0% /dev/shm tmpfs 245M 29M 217M 12% /run tmpfs 245M 0 245M 0% /sys/fs/cgroup tmpfs 49M 0 49M 0% /run/user/1000 

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There is a discrepancy between free and ps_mem. htop and top agrees with free at overall usage but the RES column looks like ps_mem results. There is at least 300M lost in my system and I can't find it.