Any tool other than Valgrind to monitor memory usage for running processes in Linux?

Question

This answer to this question says that there's no way to attach Valgrind to an already running process.
Are there any other tools for Linux that can report on memory usage but can attach to a process that's already running?

Answer 1

All app data should be in

/proc/<PID>/

Answer 2

You can use tools like pmap or ps_mem.py to get more details about the memory use of running processes than you get from top. You won't get all the fancy features from Valgrind like detecting memory leaks and such.