Does Desktop Environment effect the performance of program?

Question

I was wondering why some DE use more resources while others uses less. Does it have to do anything with performances or is it consuming more resources because of it's appearance. What's difference between light-weight DE XFCE, LXDE and other DE like KDE, UNITY?

Answer 1

Providing a more feature rich DE consumes 4 resources.

• RAM
• CPU
• Hard Drive Space
• Graphics

How a DE uses the above 4 resources is what effects the overall performance. A DE that gives you a very feature rich experience, will typically consume more of these resources than saw a light weight DE that isn't as feature rich.

For a comparison of the DE's I'd take a look at the Wikipedia article titled: Comparison of X Window System desktop environments.

Answer 2

Your DE won't affect the performance¹ of programs running within it except to the extent it consumes RAM. In other words, if you have enough RAM for both of them, the program won't perform better with KDE vs. LXDE, etc.

"Having enough RAM" doesn't necessarily mean the DE + the program = 99%. The kernel uses free RAM for caching, and if there isn't much, performance may suffer due to the lack of cache. Here's some example free output:

             total       used       free     shared    buffers     cached
Mem:       3735512    3547108     188404          0      37484    1296184
-/+ buffers/cache:    2213440    1522072
Swap:      5496148      30012    5466136

On the first line, we see a total of 373.5 MB available memory, with 354.7 used. However, 133.35 (129.6 + 3.75) MB of that are buffers or cache. This is memory that isn't actually committed; the cache can be dumped and the space can be made available on a moment's notice, so on the next line we see 354.7 - 133.35 = 221.35 MB used and 18.8 + 133.35 = 152.2 MB free.

Depending on your amount of RAM, the system may usually follow that pattern, where the RAM is completely consumed by the combination of actual commitments plus caching, indicating the kernel is maximizing its use of resources. In this situation it will probably swap a small amount of low priority stuff out (the third line). However, that maximization isn't always possible, so sometimes you may see a significant of RAM left free even when the cache is included. This may give you a clue as to just how much cache the kernel is prone to use under your circumstances. Ideally, you want to make sure that it does have enough room to do this. If you notice a lot of swap space used on the third line, you are well past that point.

Different DE's use different amounts of RAM reflecting the number and complexity of their components. This generally isn't that much on today's GB size machines, but it can add up. If you are straining the limits just described and you have <= 2GB, using a lighter DE may change that a bit. Using no DE at all (i.e., just a window manager) will change it more, because DE's must run a window manager anyway. If you have > 2GB, changing DE's probably won't change much.

Finally, most processor greedy programs aren't GUI programs. GUI programs are usually idle, waiting for user activity, or doing something of low intensity (e.g., video playback for a modern desktop is a low intensity activity; it does not require a high percentage of the available processor time). Truly greedy programs are ones which will use as much processor as they can no matter what -- get a faster processor and they will still max it out (e.g., compilers), but of course, they will complete a task more quickly. If you are really really in hurry, there may be an advantage to running those without any GUI at all, since the running GUI does demand that the scheduler be kept busy. This is not hugely significant, however.

One thing I notice frequently WRT to processor usage on a desktop is the web browser; it shouldn't be using much most of the time. If you notice it, or some plugin related to it, is constantly consuming CPU above say 1-2% (or whatever it is when you first open it), it's probably something in one of the tabs. Try closing them to see what happens.

¹ Defined as access to processor time, and taking into account the fact that without a RAM cache, this may be reduced due to waiting on disk I/O (the frequently used things that would have been cached must instead be read repeatedly from disk).