How to find the actual memory usage on Redhat Linux.

[Silver_1]

Hi,

[root@redhat1 root]# top
17:50:00 up 74 days, 5:49, 1 user, load average: 0.00, 0.01, 0.00
375 processes: 374 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 1.9% 0.0% 0.7% 0.0% 2.4% 0.2% 94.6%
cpu00 0.0% 0.0% 0.9% 0.0% 0.0% 0.0% 99.0%
cpu01 0.9% 0.0% 0.9% 0.0% 0.0% 0.0% 98.0%
cpu02 5.8% 0.0% 0.9% 0.0% 9.7% 0.0% 83.4%
cpu03 0.9% 0.0% 0.0% 0.0% 0.0% 0.9% 98.0%
Mem: 10205344k av, 10157704k used, 47640k free, 0k shrd, 129720k buff
7694616k actv, 1471124k in_d, 222456k in_c
Swap: 10485752k av, 157692k used, 10328060k free 8064472k cached



As you can see the memory is almost used 100%... is it right ?

Why i am asking is that i have some machines eventhough there is no oracle instances on this machine it shows that 3GB of memory is already used..

[RTpub]

You could try the ps command to show memory usage. See 'man ps' for details.

[Vitaly Karasik_1 · Accepted solution]

The answer is simple - linux kernel takes *all* RAM for bufferes/cache, but release it if some applications ask for memory.

See, for example, these articles:

http://forums.gentoo.org/viewtopic.php?t=175419 Linux Memory Management or 'Why is there no free RAM?'

http://www.redhat.com/magazine/001nov04/features/vm/ Understanding Virtual Memory

[Ivan Ferreira]

Yes, that is right, Linux will try to use 100% of memory always, if not used by programs, will be used as buffer/cache.

Use the "free" command to identify the memory used by programs and as buffer/cache. The values under +/- buffers/cache gives you the real memory usage.

[Jess Long]

If you want detailed usage of memory, just 'cat /proc/meminfo'.

[Silver_1]

Thanks Guys