In Linux, how to tell how much memory processes are using?

Getting right memory usage is trickier than one may think. The best way I could find is:

echo 0 $(awk '/TYPE/ {print "+", $2}' /proc/`pidof PROCESS`/smaps) | bc

Where "PROCESS" is the name of the process you want to inspect and "TYPE" is one of:

• Rss: resident memory usage, all memory the process uses, including all memory this process shares with other processes. It does not include swap;
• Shared: memory that this process shares with other processes;
• Private: private memory used by this process, you can look for memory leaks here;
• Swap: swap memory used by the process;
• Pss: Proportional Set Size, a good overall memory indicator. It is the Rss adjusted for sharing: if a process has 1MiB private and 20MiB shared between other 10 processes, Pss is 1 + 20/10 = 3MiB

Other valid values are Size (i.e. virtual size, which is almost meaningless) and Referenced (the amount of memory currently marked as referenced or accessed).

You can use watch or some other bash-script-fu to keep an eye on those values for processes that you want to monitor.

For more informations about smaps: http://www.kernel.org/doc/Documentation/filesystems/proc.txt.

I don't know why the answer seem so complicated... It seems pretty simple to do this with ps:

mem(){                                                                                                          ps -eo rss,pid,euser,args:100 --sort %mem | grep -v grep | grep -i $@ | awk '{printf $1/1024 "MB"; $1=""; print }'}

Example usage:

$ mem mysql0.511719MB 781 root /bin/sh /usr/bin/mysqld_safe0.511719MB 1124 root logger -t mysqld -p daemon.error2.53516MB 1123 mysql /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock --port=3306

Use ps to find the process id for the application, then use top -p1010 (substitute 1010 for the real process id). The RES column is the used physical memory and the VIRT column is the used virtual memory - including libraries and swapped memory.

More info can be found using "man top"