Update: Since Eclipse Mars update in Fedora 22, and with latest updates installed, the memory/CPU usage problem is fixed. Also, the problem with mylyn icons is fixed. While there are still some rendering bugs, along with some bad colors here and there; the GTK3 version is now usable for me.
Since upgrade to Fedora 22, I had several problems with Eclipse. The most annoying one, in my pretty old laptop, was nearly locking up the system after using it for awhile as reported here. I found that my 4GB RAM is almost full and kswapd is taking almost 100% CPU.
First, I suspected that it is a kernel bug since kswapd was using 100% CPU. And, it seems that it really is, but it is an old kernel problem happens when the available RAM is low. Therefore, it should not be the main reason of my problems.
Investigating more, I found the the amount of ‘shared’ memory in ‘free -m’ output keeps increasing when I use Eclipse until I’m forced to close Eclipse due to lock up. Then it is returned back to normal. I guess this is a graphics driver bug, as the Eclipse memory usage reported by ‘top’ is not changed much since its start. (and the kernel out of memory messages always happen in the driver code).
Anyway, besides, Eclipse was very ‘heavy’ on my laptop: it constantly used very high CPU usage even if I just scrolled the editor window. It was also very slow (with lag). Also Eclipse uses a new coloring for various part of the UI in F22, which are sometimes very annoying (e.g. unreadable text, unnoticeable selected region, etc). I was forced to change some colors to have a usable editor.
I was living by all these problems until yesterday, in which I found that mylyn task list is also buggy. It didn’t show unread/new issue marks beside issue icons, so I was missing new/updated issues assigned to me. I was seriously considering switching back to Fedora 21, when I suddenly found out that Eclipse is using GTK3 backend in Fedora 22 and I should be able to make it use GTK2 instead.
The first way to do this I found in Internet was setting SWT_GTK3 environment variable to 0. But it didn’t work in Fedora 22. It turns out that Eclipse has a command line argument for it, which is used by Fedora (in /etc/eclipse.ini) to force usage of GTK3 backend. So, to run Eclipse with GTK2 backend, you are forced to either modify eclipse.ini, or run eclipse with the following command line option:
eclipse --launcher.GTK_version 2
And yes, finally, it fixed all my problems with Eclipse in Fedora 22!