linux RAM

Список процессов отсортированый по потребляемой памяти

ps -eo pid,ppid,rss,vsize,pcpu,pmem,cmd -ww --sort=rss

VSIZE (Virtual memory SIZE) - The amount of memory the process is
    currently using. This includes the amount in RAM and the amount in
    swap.

    RSS (Resident Set Size) - The portion of a process that exists in
    physical memory (RAM). The rest of the program exists in swap. If
    the computer has not used swap, this number will be equal to
    VSIZE.
 

Очистить кэшированую память
# sync; echo 3 > /proc/sys/vm/drop_caches