In February 2015, Xfce 4.12 was released. The first Xfce release in nearly three years, it was greeted with enthusiasm. Yet at the same time, a few users questioned whether the new version was as light on memory as earlier releases.
It's a good question -- and by that comment, I mean, as people usually do, that it has no clear answer. Some indicators suggest that Xfce remains as efficient as ever, while others suggest Xfce is not much different from other popular desktop environments, such as KDE.
Founded in 1996, Xfce describes itself as being "fast and low on system resources, while still being visually appealing and user friendly." In other words, its goal is to be a compromise between minimalist window managers and fully equipped desktop environments like GNOME and KDE. For years, it has filled this niche to perfection, trailing a distant third among desktop environments while GNOME and KDE battled for first and second place.
However, the user revolt over GNOME 3 catapulted Xfce abruptly into a consistent second place in user polls, where it consistently takes 25-30% of the votes. This new found popularity makes the question of whether Xfce is still true to its goal seem much more relevant than it would have been five years ago. Whatever else is true, Xfce remains a classic desktop with a strong following among Linux users.
A major obstacle to answering the question is that desktop environments do not exist in isolation. At least to some extent, their requirements depends on the distribution that packages them.
For example, the fact that the KDE-based Kubuntu and the Xfce-based Xubuntu both suggest a minimum of 512 megabytes of RAM may have as much to do with both of them being based on Ubuntu than on the desktop environments that each distribution runs.
Probably, too, what matters most is not the minimal amount of RAM required, but the recommended RAM -- and both Kubuntu and Xubuntu recommend at least a gigabyte, which suggests that KDE's requirements and Xfce's may be approximately the same -- at least when running on Ubuntu-based systems.
A more promising answer is the results of the
free -m command. The command lists the total amount of memory available on the first line of its output, and the amount of memory allocated to buffers and cached memory on the second line. The amount of RAM actually used is the total of the used and unused buffers and cached memory subtracted from the available memory. The
-m option on the command gives the results in megabytes.
Run in virtual machines, each with 1024 megabytes of memory, and with only a virtual terminal open, the free command provides some concrete figures. Both the current and previous releases of Xfce register as having 412 megabytes unallocated, with, of course, the buffered and cached memory available to be released as required. This figure indicates that the current version of Xfce has not bulked up its requirements.
KDE Plasma 4.14 has only 1 megabyte unallocated, which means that, until recently, Xfce really did use less RAM. Nor has that greatly changed, since Plasma 5.2 has 8 unallocated megabytes. Despite KDE's recent efforts to reduce memory requirements, it trails the new release of Xfce. Running
free - m with
watch confirms that, as applications are opened and closed, Xfce 4.12 consistently uses less memory.
However, these results tell only part of the story. The fact that KDE Plasma 5.2 opens with 371 megabytes of buffered and cache memory compared to Xfce's 4.12 suggests that Plasma should open applications faster than Xfce -- and that does seem to be the case. For instance, while Xfce 4.12 takes six seconds apiece to open Firefox and LibreOffice, Plasma 5.2 takes just over four seconds apiece. Apparently, what matters is not just the amount of free memory, but how the allocated memory is used.
A definitive answer to how lightweight Xfce is remains elusive. However, what is even more elusive is how much a definitive answer would matter.
Given Xfce's recent popularity, it is almost certainly not being installed primarily on older systems where every byte of memory matters. On recent computers, being lightweight is as much an aesthetic choice than a necessity, and is not the only factor affecting performance.
In the last few years, many users have chosen a classical desktop, caring little about speed so long as it has a familiar, no-nonsense design. For these users, Xfce remains a prime choice, regardless of how lightweight it actually is.