we can check free memory in many ways . Below are the couple of examples on how we can check .
1) free command :-
using free command it gives current total memory allocated and current usage including cache/buffer memory usage .
[root@tstvm ~]# free -m
total used free shared buffers cached
Mem: 988 194 794 0 43 49
-/+ buffers/cache: 101 887
Swap: 1983 0 1983
[root@tstvm ~]#
from the above example
988 gb = total memory allocated
194 gb = current used memory
794 gb = current free memory
43 and 49 is buffer/cache memory .
NOTE:- Linux uses free memory for
buffer/cache to keep data read/write from/to disks in memory for speed access
in the future.These memory can be reclaimed in
case kernel/application needs to allocation explicitly.
2) cat /proc/meminfo
[root@tstvm ~]# cat /proc/meminfo
MemTotal: 1012548 kB
MemFree: 813080 kB
Buffers: 44428 kB
Cached: 50812 kB
SwapCached: 0 kB
Active: 67108 kB
Inactive: 44864 kB
Active(anon): 16968 kB
Inactive(anon): 4 kB
Active(file): 50140 kB
Inactive(file): 44860 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 2031608 kB
SwapFree: 2031608 kB
Dirty: 8 kB
Writeback: 0 kB
AnonPages: 16752 kB
Mapped: 11060 kB
Shmem: 236 kB
Slab: 64652 kB
SReclaimable: 12612 kB
SUnreclaim: 52040 kB
KernelStack: 776 kB
PageTables: 2912 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 2537880 kB
Committed_AS: 103460 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 276296 kB
VmallocChunk: 34359446148 kB
HardwareCorrupted: 0 kB
AnonHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 6144 kB
DirectMap2M: 1042432 kB
DirectMap1G: 0 kB
[root@tstvm ~]#
Active memory is the amount of buffer and cache memory has been recently used, which is not usually reclaimed
Inactive memory is the amount of buffer and cache memory that has not been recently used, can be reclaimed by kernel
3) TOP command :-
using top command you can see memory/cpu usage including the current running process. you can the each process and that perticular process memory/cpu usage .
top - 07:48:08 up 21 min, 1 user, load average: 0.00, 0.00, 0.02
Tasks: 89 total, 1 running, 88 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.3%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1012548k total, 199864k used, 812684k free, 44456k buffers
Swap: 2031608k total, 0k used, 2031608k free, 51072k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 19356 1524 1224 S 0.0 0.2 0:01.71 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
4 root 20 0 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
6 root RT 0 0 0 0 S 0.0 0.0 0:00.01 watchdog/0
7 root 20 0 0 0 0 S 0.0 0.0 0:02.26 events/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cgroup
9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper
10 root 20 0 0 0 0 S 0.0 0.0 0:00.00 netns
11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 async/mgr
12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pm
13 root 20 0 0 0 0 S 0.0 0.0 0:00.01 sync_supers
14 root 20 0 0 0 0 S 0.0 0.0 0:00.01 bdi-default
15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/0
16 root 20 0 0 0 0 S 0.0 0.0 0:00.20 kblockd/0
17 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpid
18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_notify
19 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_hotplug
20 root 20 0 0 0 0 S 0.0 0.0 0:00.03 ata/0
21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata_aux
22 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksuspend_usbd
23 root 20 0 0 0 0 S 0.0 0.0 0:00.17 khubd
24 root 20 0 0 0 0 S 0.0 0.0 0:00.02 kseriod
25 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md/0
26 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md_misc/0
27 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khungtaskd
28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kswapd0
29 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
30 root 39 19 0 0 0 S 0.0 0.0 0:00.00 khugepaged
31 root 20 0 0 0 0 S 0.0 0.0 0:00.00 aio/0
32 root 20 0 0 0 0 S 0.0 0.0 0:00.00 crypto/0
37 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthrotld/0
38 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pciehpd
40 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kpsmoused
41 root 20 0 0 0 0 S 0.0 0.0 0:00.00 usbhid_resumer
72 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kstriped
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