[dapper] Memory and CPU usage

Marius Gedminas marius at pov.lt
Tue Jan 31 10:00:43 UTC 2006

On Tue, Jan 31, 2006 at 04:20:41PM +1100, Sasha Tsykin wrote:
> I've checked both ksysguard and the gnome system monitor. When running 
> side by side, they give different results. They show the same 
> application using radically different amounts of memory (eg. 
> gnome-system monitor shows mozilla-thunderbird-bin using 62.7MiB but 
> ksysguard shows it using ~265MiB).

I would guess that one of them is showing virtual memory size, while the
other is showing RSS (resident set size).  RSS = VIRT minus those pages
that were swapped out and minus those pages from libraries/executables/
other memory-mapped files that are not loaded from disk (e.g., because
they were never accessed yet).

Both numbers are slightly misleading, by the way, since the same shared
libraries can be included in process sizes for several different
processes, although only one copy of the library is loaded into memory.
If you want to learn more about why measuring memory usage accurately is
difficuly, you may want to read these posts:

I've never used ksysguard, but you can ask gnome-system-monitor to show
all sorts of columns, including virtual memory, RSS, and CPU usage.

> Also, ksysguard which is the only one 
> of the two which reports CPU utilization reports almost all my 
> applications using 0% of my CPU.

You can ask gnome-system-monitor to report CPU utilization for each

(Note that sometimes you might want to ask gnome-system-monitor to show
all processes rather than just the ones you own.)

Marius Gedminas
The last good thing written in C was Franz Schubert's Symphony #9.
        -- Erwin Dietrich
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