KWin

From LinuxReviews

KWin is an advanced window manager for the X Window System designed to be used as part of the K Desktop Environment (KDE),

Compositing

KWin supports advanced composite effects as of KDE 4.

Nvidia

It's been said that KWin performs better on nvidia based cards when using OpenGL with shared memory^[1]

This can be configured in systemsettings -> Desktop -> Desktop Effects -> Advanced.