Posts Tagged ‘memory’

linux server memory management

February 27th, 2011 Comments off

It has been long time since last post, but finally something useful shown up, today I want to present simple script for monitoring memory in Linux.

But first happy news: our server is now sucessfully migrated to nginx, no more apache, now maximal memory usage is 20MB per process.

So here is script, it is almost simple, find some processes, and kill them if to much RAM used:


memory=$(free -m | awk '{if (FNR==2) print $2}')
count=$(ps aux | awk -v threshold=$threshold '{if (FNR==1 || $4>=threshold) print}' | tee $log | wc -l)
[ $count -gt 1 ] && echo "Showing processes over ${threshold_mb}MB, killing processes over ${kill_at_mb}MB" && cat $log

cat $log | awk -v kill_at=$kill_at '{if ($4>kill_at) print $2" "$4 }' | while read pid mem;
used_mb=$(($(echo $mem | sed 's/\.//')*memory/1000))
# fix rounding problem in awk
if [ $used_mb -gt $kill_at_mb ]; then
kill -9 $pid
echo "pid $pid used ${used_mb}MB - killed"
rm -f $log

Most important in this script are first two variables, threshold_mb which is a limit for showing processes (it is rough comparison) and kill_at_mb which is limit for killing processes, by default this limit is 5 times bigger then showing threshold. Cause killing is more important operation additional check for used memory is more strict to be sure, only processes over the limit are killed.

Save it to disk and in crontab:

sudo crontab -e

add the following lines:

MAILTO=<your @email>
* * * * * /root/bin/

That’s all, now add some filter in your mailbox to ignore mails form server – this is all automatic, but you might want to have this for later check if some important processes are missing.