Useful Linux Memory Calculation Commands

Calculate total memory used by apps

ps aux | awk '{sum+=$6} END {print sum / 1024}’

To free pagecache:

    echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:

    echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:

    echo 3 > /proc/sys/vm/drop_caches

dd physical memory being used by a user, in this it’s user daemon

ps aux |awk '{if($1 ~ "daemon"){Total+=$6}} END {print Total/1024" MB"}'

see how many processes are using swap:

grep Swap /proc/[1-9]*/smaps | grep -v '\W0 kB'

list the top 10 processes using the most swap:

ps ax | sed "s/^ *//" > /tmp/ps_ax.output 
for x in $(grep Swap /proc/[1-9]*/smaps | grep -v '\W0 kB' | tr -s ' ' | cut -d' ' -f-2 | sort -t' ' -k2 -n | tr -d ' ' | tail -10); do 
    swapusage=$(echo $x | cut -d: -f3)
    pid=$(echo $x | cut -d/ -f3)
    procname=$(cat /tmp/ps_ax.output | grep ^$pid)
    echo "============================" 
    echo "Process   : $procname" 
    echo "Swap usage: $swapusage kB"; done

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