Get a summary of per process memory usage using awk (php-fpm for example). Note, if a process shares libraries, they will be counted multiple times so this isn't perfect; however, it should give you a good rough summary of the amount of memory used.

perProcessMemorySummary.sh

ps aux | fgrep php-fpm | egrep -v 'master process|fgrep' | sort -k13 | awk '{print $1,$6}' | awk '{a[$1]+=$2;}END{for(i in a)print i, a[i] * 0.001;}' | sort -nr -k2 | awk '{ sum+=$2 ; print $1, $2, " MB"} END {print "Total Memory Usage:", sum, " MB"}'

sampleResults.txt

lilnbboj 268.368  MB
zkrmkprl 221.532  MB
yfjoubng 212.532  MB
rjnjpbqg 209.78  MB
dvpqmqss 141.96  MB
paxsqasd 130.288  MB
lgtuwbau 118.284  MB
bgougjoq 117.36  MB
mhffauvt 30.292  MB
wxsdlnag 30.28  MB
tillfpoo 30.28  MB
bbsahigr 18.18  MB
ariorpev 18.168  MB
ulzmupsw 18.16  MB
uxtodijm 18.156  MB
njqugpvs 18.156  MB
mvldssjn 18.156  MB
dzhsazkm 18.152  MB
wuruxrrn 18.144  MB
goulhkdr 18.144  MB
xhhlhxag 18.132  MB
ujepetxu 18.132  MB
rtagkhxk 18.124  MB
Total Memory Usage: 1728.76  MB