I need to check memory usage & availability before I could run a program if there is enough memory is left or not, so how could i achieve this? Which command output i should rely on? I have diplayed outputs of SAR, VMstat and PRstat commands below, But how could i check memory usage according to total mem?
For example i have tried this directingSAR output to a file, however i can't compare it to total memory. How could i proceed? should i use "prtconf | grep -i mem" output to compare the value below?
cat 123.txt | nawk '/Average/{print $2}'
Output of VMSTAT for Memoru Usage Status of Virtual Machine
-bash-3.00$ vmstat 4 5
kthr memory page disk faults cpu
r b w swap free re mf pi po fr de sr s0 s1 s2 -- in sy cs us sy id
0 0 0 37855508 28701468 31 49 49 0 0 0 0 -0 4 -0 0 2247 2054 1087 0 1 98
0 0 0 30946784 26165180 3 14 0 0 0 0 0 0 6 0 0 2798 2554 1497 1 0 99
0 0 0 30946632 26164856 0 4 0 0 0 0 0 0 3 0 0 2927 3488 1825 1 2 97
0 0 0 30946632 26164308 0 2 0 0 0 0 0 0 12 0 0 5979 8694 4221 2 2 96
0 0 0 30946632 26164040 0 0 0 0 0 0 0 0 4 0 0 3630 4079 2333 1 1 98
Output of PRSTAT command which give process status based on users.
-bash-3.00$ prstat -u sscm -a -s cpu 0 1 | sed -e '/^$/d;/sleep/d;/Total/d'
PID USERNAME SIZE RSS STATE PRI NICE TIME CPU PROCESS/NLWP
26306 sscm 3492K 2668K cpu7 59 0 0:00:00 0.0% prstat/1
NPROC USERNAME SWAP RSS MEMORY TIME CPU
13 sscm 25G 8581M 17% 69:43:21 1.3%
In the output of vmstat the free memory is in KB, the sar output is in pages.
bash-3.2$ sar -r 1 1
SunOS <name> 5.10 Generic_147440-09 sun4v 05/26/2014
14:23:00 freemem freeswap
14:23:01 10776773 203955648
bash-3.2$ pagesize
8192
bash-3.2$ echo '10776773*8/1024' | bc
84193
bash-3.2$ vmstat 1 1
kthr memory page disk faults cpu
r b w swap free re mf pi po fr de sr lf s0 s4 s5 in sy cs us sy id
0 0 0 101746080 85650520 267 1364 0 0 0 0 0 0 -0 -0 7 5002 17103 5156 0 0 99
The above shows 81/82GB of free ram.
You're running Solaris x86, so you have a pagesize of 4K:
$ echo '6541638*4/1024' | bc
25553
$ echo 26164040/1024 | bc
25550
EDIT: Corrected, see jlliagre's post below. The above output shows 24GB of free RAM.
Use /usr/sbin/prtconf|fgrep Memory to check the total installed RAM.
I did not know this command before but it really looks good to me.
I could run it as root user and it gave me an output like the following, however i may not be allowed to use root user permission to run such commands in production. What is the difference between free list and cache list? shall i consider the %Tot column for "Free" page sum?
You have plenty of RAM available (62%), the freelist is unused RAM and contains nothing of interest while the cachelist, despite also being unused RAM contains data from previously accessed files. If these files are read again, the data will be picked from that memory saving I/Os.
Well, I suppose the output of sar/vmstat and mdb are not sampled at the same time (or they are from different systems).
I'd expect the freelist (mdb) and free (vmstat) to be almost equal ...,
or I'm missing something?