Adam Williamson from happyassasin.net has a nice article titled Some comparisons between Fedora 13, 15, 17, 19 and 20. Adam works for Red Hat as Fedora QA Community Manager, meaning he knows what he’s taking about:
We can see that the memory used when you simply boot to a console and log in has changed very little all the way back to Fedora 13, released 2010-05-25. We’re doing a fairly good job of keeping our base system from bloating excessively. 19 and 20 are both 30MB worse than 17, but then, 17 was 25MB better than 15.
The same certainly doesn’t hold true for the graphical desktop, though. Just sitting at a mostly-idle desktop with a terminal open, our memory usage has gone from 275MB under the ancien GNOME 2 regime to 300MB with GNOME 3′s ‘fallback mode’ (which was more or less GNOME 2), then rocketed to nearly 400MB, 535MB, and nearly 700MB in subsequent releases. I haven’t yet looked in detail at the changes, but I did take screenshots of ‘top’ ordered by memory usage for each install.
The measurements are done using free command in a gnome-terminal immediately after bootup. GNOME runs in a virtual machine without hardware acceleration, and it ends up using Mesa llvmpipe driver. These are the graphs based on Adam’s measurements:
It is a valid setup, GNOME fully supports software rendering using Mesa 3D Graphics Library. The feature was introduced in Fedora 17 and it is officially described by Fedora/GNOME team here. This feature replaced the fallback mode from previous releases.
If you run GNOME on a system with a fully supported hardware accelerated video card, the numbers will be much smaller. Looks like Adam hit the worst-case scenario with his tests. He continues:
the memory usage of the [GNOME] Shell itself grew massively – in fact, more than doubled – from Fedora 19 to Fedora 20, accounting for all the overall increase in memory usage from 19 to 20 by itself. gnome-settings-daemon has also been growing on a more modest scale, from 18MB at F15 to 30MB in F20.
I don’t know if anyone in GNOME land is focused on efficiency, but these numbers suggest that it might be a good idea to spend some time on it. Some of the increase is probably unavoidable with GNOME’s increase in capabilities over time, but some of it is probably fixable.
As a side note, there are plenty of other desktop environments and window managers in Linux. There are also lots of other Linux distributions. Not all of them are created equal, but none requires 700MB to run an empty desktop. Below is just a small sample of what is available (measurements on real hardware, free command in a terminal after bootup):