free physical memory

saavik · 08-25-2005, 04:29 AM

Hello!

I simply would like to find out how much physical memory is free on my server ?

Something like 'free -m'

Thanks !

jlliagre · 08-25-2005, 06:11 AM

vmstat's column "free" reports free physical memory available.
ignore the first sample, as it's the average since last reboot.

nixcraft · 08-25-2005, 12:21 PM

Yup use vmstat or prtconf as described here :
http://www.cyberciti.biz/nixcraft/vi...mation-or.html

jlliagre · 08-25-2005, 01:00 PM

prtconf doesn't report free memory but installed memory.

saavik · 08-26-2005, 06:40 AM

what vmstat says:

procs memory page disk faults cpu
r b w swap free re mf pi po fr de sr s6 sd sd sd in sy cs us sy id
0 0 0 12860632 5120448 114 590 631 1 1 0 0 0 4 4 8 77 148 324 79 16 5
0 0 0 12676104 4893432 1 368 0 0 0 0 0 0 7 5 6 5017 14614 9011 31 7 62
0 0 0 12676072 4893400 0 197 0 0 0 0 0 0 1 1 7 3619 13456 8272 21 6 73

so the last line would sys I have 4893400 kb of free memory.

so 4893400 / 1024 = 4778 MB free ????

How do I get to MB ?

jlliagre · 08-26-2005, 10:30 AM

Quote:

so 4893400 / 1024 = 4778 MB free ????

Precisely, you have 4.66 GB free.

Here's the bigger

machine I'm currently running:

I has 48 Gigabytes of RAM

Code:

$ prtconf | head -2
System Configuration:  Sun Microsystems  sun4u
Memory size: 49152 Megabytes

It has plenty of that memory currently unused:

Code:

 $ vmstat 1 2
 procs     memory            page            disk          faults      cpu
 r b w   swap  free  re  mf pi po fr de sr s0 s1 s3 s3   in   sy   cs us sy id
 0 0 0 46338392 43237520 10 44 7 4 4  0  0  1  1  2  1  327 1638  518  1  0 99
 0 0 0 49814392 47284968 0 8 0  0  0  0  0  0  0  0  0  302  328  458  0  0 100

which I can convert to 46176 MB or 45.09 GB.

Code:

$ bc
scale=2
47284968/1024
46176.72
47284968/1024/1024
45.09

My laptop is less lucky:

Code:

$ prtconf -v | head -2
System Configuration:  Sun Microsystems  i86pc
Memory size: 511 Megabytes
$ vmstat 1 2
 kthr      memory            page            disk          faults      cpu
 r b w   swap  free  re  mf pi po fr de sr cd s0 -- --   in   sy   cs us sy id
 0 0 0 865600 254276 15  97  9  0  0  0 11  2  0  0  0  269 1088  381  9  2 89
 0 0 0 837036 221256  0   7  0  0  0  0  0  0  0  0  0  311 2334  534  6  0 94

216 MB free ...

sundialsvcs · 08-26-2005, 11:49 AM

Incidentally, it is a Good Thing for physical memory to be as full as possible. If there's anything out there that it could contain, then it is advantageous for something to be there.

Linux will naturally use "free" memory for buffers of various sorts .. so-called shared memory. As the system begins to experience memory pressure, that allocation may start to go down, because buffers are a lower-priority use of memory.

The key performance-figure is to observe, not so much "what is the system is doing," but "who is experiencing pain because of it?" How many processes are experiencing substantial involuntary waits due to paging? How many of them are unable to achieve keeping their working-sets (the amount of memory they would like to have right now) in-memory? You need to somewhat-disregard the behavior that an application may experience while it is starting-up, but when it is stable and has been running for a minute or so, you can tell if it's "crying" or not.

jlliagre · 08-26-2005, 12:22 PM

No doubt maximizing memory use is a "Good Thing" (tm), and Solaris is pretty efficient at it.
That said, when you have 48 Gigabytes, on a quiet day that's hard to fill ...