You can find the memory used by a program (process) by looking into /proc directory or using standard command such as ps or top. However, you must calculate all memory usage by hand i.e. add Shared Memory + mapped file + total virtual memory size of the process + Resident Set Size + non-swapped physical memory used by process.

So how do you find the memory used by a process or program under Linux? Use a tool called pmap. It reports the memory map of a process or processes.

pmap examples

To display process mappings, type
$ pmap pid
$ pmap 3724
Output:

3724:   /usr/sbin/lighttpd -f /etc/lighttpd/lighttpd.conf
0000000000400000    164K r-x--  /usr/sbin/lighttpd
0000000000629000     12K rw---  /usr/sbin/lighttpd
000000000bb6b000   4240K rw---    [ anon ]
00000035ee600000    104K r-x--  /lib64/ld-2.5.so
00000035ee819000      4K r----  /lib64/ld-2.5.so
00000035ee81a000      4K rw---  /lib64/ld-2.5.so
00000035eea00000   1304K r-x--  /lib64/libc-2.5.so
00000035eeb46000   2048K -----  /lib64/libc-2.5.so
00000035eed46000     16K r----  /lib64/libc-2.5.so
00000035eed4a000      4K rw---  /lib64/libc-2.5.so
00000035eed4b000     20K rw---    [ anon ]
00000035eee00000      8K r-x--  /lib64/libdl-2.5.so
00000035eee02000   2048K -----  /lib64/libdl-2.5.so
.....
....
00002aaaac51e000      4K r----  /lib64/libnss_files-2.5.so
00002aaaac51f000      4K rw---  /lib64/libnss_files-2.5.so
00007fff7143b000     84K rw---    [ stack ]
ffffffffff600000   8192K -----    [ anon ]
 total            75180K

The -x option can be used to provide information about the memory allocation and mapping types per mapping. The amount of resident, non-shared anonymous, and locked memory is shown for each mapping:
pmap -x 3526
Output:

3526:   -bash
Address           Kbytes     RSS    Anon  Locked Mode   Mapping
0000000000400000     700       -       -       - r-x--  bash
00000000006ae000      40       -       -       - rw---  bash
00000000006b8000      20       -       -       - rw---    [ anon ]
00000000008b7000      32       -       -       - rw---  bash
00000000098de000     536       -       -       - rw---    [ anon ]
00000035ee600000     104       -       -       - r-x--  ld-2.5.so
00000035ee819000       4       -       -       - r----  ld-2.5.so
00000035ee81a000       4       -       -       - rw---  ld-2.5.so
00000035eea00000    1304       -       -       - r-x--  libc-2.5.so
00000035eeb46000    2048       -       -       - -----  libc-2.5.so
00000035eed46000      16       -       -       - r----  libc-2.5.so
00000035eed4a000       4       -       -       - rw---  libc-2.5.so
00000035eed4b000      20       -       -       - rw---    [ anon ]
00000035eee00000       8       -       -       - r-x--  libdl-2.5.so
00000035eee02000    2048       -       -       - -----  libdl-2.5.so
00000035ef002000       4       -       -       - r----  libdl-2.5.so
00000035ef003000       4       -       -       - rw---  libdl-2.5.so
00000035ef600000      12       -       -       - r-x--  libtermcap.so.2.0.8
00000035ef603000    2044       -       -       - -----  libtermcap.so.2.0.8
00000035ef802000       4       -       -       - rw---  libtermcap.so.2.0.8
00002aaaaaaab000       4       -       -       - rw---    [ anon ]
00002aaaaaaba000      12       -       -       - rw---    [ anon ]
00002aaaaaabd000      40       -       -       - r-x--  libnss_files-2.5.so
00002aaaaaac7000    2044       -       -       - -----  libnss_files-2.5.so
00002aaaaacc6000       4       -       -       - r----  libnss_files-2.5.so
00002aaaaacc7000       4       -       -       - rw---  libnss_files-2.5.so
00002aaaaacc8000   55112       -       -       - r----  locale-archive
00002aaaae29a000      28       -       -       - r--s-  gconv-modules.cache
00002aaaae2a1000       8       -       -       - rw---    [ anon ]
00007fff9bff4000      92       -       -       - rw---    [ stack ]
ffffffffff600000    8192       -       -       - -----    [ anon ]
----------------  ------  ------  ------  ------
total kB           74496       -       -       -