Detailed analyse of memory usage
Since you seem interested about RAM, rather than flash usage, I suggest
you look at the symbol table of your compiled program, which will be
more telling than the disassembly. On my Linux system, I usually do the
following:

avr-nm -Crtd --size-sort the_program.elf | grep -i ' [dbv] '


avr-nm is the utility for displaying the symbol table. It is normally
packaged with the Arduino IDE. It is invoked here with the following
options:


--size-sort is quite explicit
-C means “demangle the C++ names”
-r means “reverse sort”, i.e. sort from largest to smallest
-td means “display numbers in decimal rather than hexadecimal”


This will output the list of all symbols that have a size, in three
columns: size, type and name. You are only interested in the symbols
that consume RAM, i.e. those of type b (BSS, or uninitialized data),
d (initialized data) and v (vtable), either in upper or lower case.
The grep command is a standard Unix utility which is used here to
extract only the relevant lines from the output of avr-nm.

Example output for a small program:

00000068 B tx_buffer
00000068 B rx_buffer
00000034 B Serial
00000016 V vtable for HardwareSerial
00000004 B timer0_overflow_count
00000004 B timer0_millis
00000002 b loop::last_print
00000001 b timer0_fract


The first 4 entries come from the Serial object. The 3 entries
starting with timer0_ are used by the Arduino timekeeping functions
(millis(), micros() and delay()). The entry named
loop::last_print is a static local variable I declared in loop().