My question is very similar to Stack Overflow question Gigantic Tabs in Eclipse on Ubuntu.
I have tried the solutions presented, but they appear to be old.
You may try the theme from https://github.com/jeeeyul/eclipse-themes.
After install this theme, apply it by choosing the theme in Window > Preferences > General > Appearence > Jeeeyul's themes.
And to solve the large tab problem, please refer to https://github.com/jeeeyul/eclipse-themes/wiki/Linux-Huge-Toolbar-Problem.
It's easy and beatiful. Enjoy it!