For an interactive analysis, you can use htop, then hit function key F6 to choose the sort-order, e.g. PERCENT_CPUPERCENT_MEM (memory usage in percents), M_RESIDENT (resident memory size, the real memory that is used), M_SIZE (virtual memory size) or M_SHARE (size of shared memory). The first two are the relevant numbers.
The green lines are threads. Hit (upper case) K and H to hide them.