How to find out how much memory a program taking

Question

I use htop to watch my processes, but most of services ran are multi threaded, so they are shown on several lines with a % of memory use which in some cases is the same for all, sometimes it varies among them.

Say in the case of Firefox it can list 15 processes each consuming 13% of memory.

Can I know hoc much memory is Firefox, MySQL, some fcgi script or anything is consuming? since the htop output seems misleading.

Answer 1

Most top implementations have a way to turn the display of threads on or off.

• htop: in the “Setup / Display options” menu, “Hide userlands threads”.
• Linux top: press H to toggle the showing of threads (but they're off by default).
• OpenBSD top: press T to toggle the showing of threads (but they're off by default).

Note that memory mappings, and hence memory occupation, is a property of a process, so you'll always see the same numbers for every thread in a process. If you see different numbers, it means there are multiple processes.

There's no easy way to find out the total memory consumption of a set of processes because the concept isn't well-defined. Some of the memory may be shared; this happens all the time with shared libraries, and in addition related processes (such as multiple instances of a server) are more likely to use shared memory to exchange data. If you just add the figures, you'll often get a number that's a lot larger than the actual used memory.

Answer 2

You could use this: http://www.pixelbeat.org/scripts/ps_mem.py