Measuring Memory Use

debian:/home/rasmus# ps ef -o command,vsize,rss,size -C php-fpm
COMMAND                        VSZ   RSS  SIZE
php-fpm: master process (/u 459152  9912  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304
 \_ php-fpm: pool www       459152  7732  3304

top isn't helpful either

debian:/home/rasmus# top -p $(pgrep -d , php-fpm)
top - 07:04:14 up 19 days, 15:21,  1 user,  load average: 0.00, 0.04, 0.51
Tasks:  11 total,   0 running,  11 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.0 us,  0.0 sy,  0.0 ni, 99.9 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem:  16355868 total, 15789244 used,   566624 free,   493148 buffers
KiB Swap:        0 total,        0 used,        0 free. 13514376 cached Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                                                                    
13950 root      20   0  459152   9912   6016 S   0.0  0.1   0:00.02 php-fpm                                                                    
13951 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13952 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13953 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13954 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13955 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13956 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13957 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13958 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13959 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm                                                                    
13960 www-data  20   0  459152   7732   3836 S   0.0  0.0   0:00.00 php-fpm 

smem!

debian:/home/rasmus# smem -t -k -U www-data -P ".*php-fpm"
  PID User     Command                         Swap      USS      PSS      RSS 
12570 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12571 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12572 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12573 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12574 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12575 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12576 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12577 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12578 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
12579 www-data php-fpm: pool www                  0   156.0K   621.0K     7.6M 
-------------------------------------------------------------------------------
   10 1                                           0     1.5M     6.1M    75.9M 

Serving Drupal 8

debian:/home/rasmus# smem -t -k -U www-data -P ".*php-fpm"
  PID User     Command                         Swap      USS      PSS      RSS 
13233 www-data php-fpm: pool www                  0   792.0K     1.3M     9.2M 
13231 www-data php-fpm: pool www                  0   792.0K     1.3M     9.2M 
13235 www-data php-fpm: pool www                  0   792.0K     1.3M     9.2M 
13232 www-data php-fpm: pool www                  0   796.0K     1.3M     9.2M 
13234 www-data php-fpm: pool www                  0   792.0K     1.3M     9.3M 
13227 www-data php-fpm: pool www                  0   808.0K     1.3M     9.2M 
13229 www-data php-fpm: pool www                  0   808.0K     1.3M     9.2M 
13230 www-data php-fpm: pool www                  0   808.0K     1.3M     9.2M 
13226 www-data php-fpm: pool www                  0   808.0K     1.3M     9.2M 
13228 www-data php-fpm: pool www                  0   808.0K     1.3M     9.3M 
-------------------------------------------------------------------------------
   10 1                                           0     7.8M    12.9M    92.4M