On 08/22/2016 07:53 AM, correomm wrote:

Hello,

The last weekend, the VM with CentOS 7 (kernel-3.10.0-327.28.2.el7.x86_64) was running with 2.5GB of used memory, but without users connected, and heavy services running. Three minutes after reboot, the o.s. is running with 114MB used. ¿Why the 62% of memory is used if the o.s. does not have an intensive load?

top sorted by memory:

top - 12:55:34 up 8 days, 21:41, 1 user, load average: 0.16, 0.74, 0.49 Tasks: 90 total, 1 running, 89 sleeping, 0 stopped, 0 zombie %Cpu0 : 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 3882816 total, 310948 free, 2639892 used, 931976 buff/cache KiB Swap: 7815164 total, 7815164 free, 0 used. 825004 avail Mem

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 579 root 20 0 323592 23168 6232 S 0.0 0.6 0:30.07 firewalld 1110 root 20 0 553052 18264 5624 S 0.0 0.5 3:29.65 tuned 720 polkitd 20 0 530364 10900 4736 S 0.0 0.3 0:12.84 polkitd 587 root 20 0 250252 8060 4800 S 0.7 0.2 20:48.88 vmtoolsd 692 root 20 0 436892 7988 6156 S 0.0 0.2 0:12.36 NetworkManager 1 root 20 0 273832 7128 3820 S 0.0 0.2 2:20.92 systemd 577 root 20 0 210456 5488 3708 S 0.0 0.1 0:03.85 abrtd 26833 root 20 0 143008 5436 4148 S 0.0 0.1 0:13.47 sshd 487 root 20 0 46424 5112 2652 S 0.0 0.1 0:02.26 systemd-udevd 592 root 20 0 207976 4480 3124 S 0.0 0.1 0:02.31 abrt-watch-log 1806 postfix 20 0 93512 4088 3028 S 0.0 0.1 0:02.80 qmgr 470 root 20 0 129132 3956 2456 S 0.0 0.1 0:00.02 lvmetad 580 root 20 0 445712 3888 3156 S 0.0 0.1 1:00.74 rsyslogd 26950 postfix 20 0 93328 3848 2840 S 0.0 0.1 0:00.11 pickup 1112 root 20 0 82560 3544 2688 S 0.0 0.1 1:02.99 sshd 26837 root 20 0 116160 2976 1732 S 0.0 0.1 0:01.94 bash 719 root 20 0 53064 2644 2052 S 0.0 0.1 0:00.25 wpa_supplicant 26783 root 20 0 178108 2448 1520 S 0.0 0.1 0:00.07 crond 578 root 20 0 130060 2184 1672 S 0.0 0.1 0:00.66 smartd 1801 root 20 0 93224 2168 1116 S 0.0 0.1 0:11.25 master 27041 root 20 0 157688 2128 1448 R 1.4 0.1 0:00.51 top 581 dbus 20 0 37112 2116 1392 S 0.0 0.1 0:28.27 dbus-daemon 26968 root 20 0 36820 2076 1812 S 0.0 0.1 0:00.69 systemd-journal 608 chrony 20 0 115844 1860 1448 S 0.0 0.0 0:14.59 chronyd 586 root 20 0 26448 1700 1348 S 0.0 0.0 0:46.24 systemd-logind 615 root 20 0 126336 1680 1028 S 0.0 0.0 0:21.39 crond 555 root 16 -4 116724 1604 1208 S 0.0 0.0 0:33.97 auditd 26787 root 20 0 113120 1404 1220 S 0.0 0.0 0:00.05 freshclam-sleep 620 root 20 0 25964 952 752 S 0.0 0.0 0:00.62 atd 18160 root 20 0 110036 816 692 S 0.0 0.0 0:00.18 agetty 601 libstor+ 20 0 8532 780 632 S 0.0 0.0 0:10.61 lsmd 26792 root 20 0 107896 620 528 S 0.0 0.0 0:00.00 sleep 2 root 20 0 0 0 0 S 0.0 0.0 0:00.24 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:06.40 ksoftirqd/0

# netstat -nao Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State Timer tcp 0 0 127.0.0.1:10025 0.0.0.0:* LISTEN off (0.00/0/0) tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN off (0.00/0/0) tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN off (0.00/0/0) tcp 0 64 ip.ad.dr.ess:22 my.ip.by.myisp:50470 ESTABLISHED on (0.26/0/0) tcp6 0 0 :::22 :::* LISTEN off (0.00/0/0) tcp6 0 0 ::1:25 :::* LISTEN off (0.00/0/0) udp 0 0 127.0.0.1:323 0.0.0.0:* off (0.00/0/0) udp6 0 0 ::1:323 :::* off (0.00/0/0) raw6 0 0 :::58 :::* 7 off (0.00/0/0) Active UNIX domain sockets (servers and established) Proto RefCnt Flags Type State I-Node Path unix 2 [ ACC ] STREAM LISTENING 9979 /run/lvm/lvmpolld.socket unix 2 [ ACC ] STREAM LISTENING 9988 /run/lvm/lvmetad.socket unix 2 [ ] DGRAM 6664 /run/systemd/notify unix 2 [ ACC ] STREAM LISTENING 17787 private/tlsmgr unix 2 [ ACC ] STREAM LISTENING 17790 private/rewrite unix 2 [ ACC ] STREAM LISTENING 17793 private/bounce unix 2 [ ACC ] STREAM LISTENING 6676 /run/systemd/journal/stdout unix 2 [ ACC ] STREAM LISTENING 17796 private/defer unix 2 [ ACC ] STREAM LISTENING 17799 private/trace unix 5 [ ] DGRAM 6679 /run/systemd/journal/socket unix 2 [ ACC ] STREAM LISTENING 17802 private/verify unix 11 [ ] DGRAM 6681 /dev/log unix 2 [ ACC ] STREAM LISTENING 17805 public/flush unix 2 [ ACC ] STREAM LISTENING 17808 private/proxymap unix 2 [ ACC ] STREAM LISTENING 17811 private/proxywrite unix 2 [ ACC ] STREAM LISTENING 17814 private/smtp _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

CentOS, as well as all versions of Linux, uses buffer and cache with free RAM. You have alomst 1GB of RAM used as buffer/cache in the above top.

If programs need more memory than 'free', it will be taken from the buffer/cache.