Per-process memory usage
There are several metrics to measure the amount of memory a process is using. I will begin with the two that are easiest to obtain— the virtual set size (vss) and the resident memory size (rss), both of which are available in most implementations of the ps
and top
commands:
- Vss: called VSZ in the
ps
command and VIRT intop
, is the total amount of memory mapped by a process. It is the sum of all the regions shown in/proc/<PID>/map
. This number is of limited interest, since only part of the virtual memory is committed to physical memory at any one time. - Rss: called RSS in
ps
and RES intop
, is the sum of memory that is mapped to physical pages of memory. This gets closer to the actual memory budget of the process, but there is a problem, if you add up the Rss of all the processes, you will get an overestimate the memory in use because some pages will be shared.
Using top and ps
The versions of top
and ps
from BusyBox give very limited information. The examples...