TOP – memory explanation

(just few notes – to avoid to forget)

  • VIRT: not really relevant nowadays. It’s the memory that the process could use. But the OS loads only what needed, so rarely really used. On 32bit OS, it could be the only time when you need to keep an eye as the OS can allocate up to 2-3GB only.
  • RES: Resident Set Size memory – this is the actual memory in RAM. On low used machines, it might still show high usage even if not utilised as the process to free-up the memory costs more than leaving it. In fact, Linux OS tends to use as much memory available (“unused memory is wasted memory“).
  • SH: this is the shared memory which generally contains libraries etc