Very large tabs in Eclipse panes on Ubuntu

You can edit Eclipse’s CSS instead of messing with the GTK theme.

In your Eclipse directory find the file plugins/org.eclipse.platform_4.2.*/css/e4_default_gtk.css (there’s an * in there, because I guess that the version may change in the future or may be different already). In this file there’s a CSS class:

.MPartStack {
    font-size: 11;
    swt-simple: false;
    swt-mru-visible: false;
}

And you have two possible solutions:

1. change font-size to something smaller
2. just comment out or remove font-size from this class (works well for me)

And that should do the trick.