How to check the memory usage of a process in Linux

Check how much memory a single process uses. RSS is resident (physical) memory; VSZ is the larger virtual size. pmap breaks it down by mapping.

# Top processes by resident memory (RSS)
ps -eo pid,user,rss,vsz,comm --sort=-rss | head -n 11

# One process, sizes in KB
ps -o pid,rss,vsz,comm -p <pid>

# Detailed memory map, with a total on the last line
pmap -x <pid> | tail -n 1
pmap -x <pid>