Comment 1 for bug 1713746

Can confirm the bug in Stretch. glxgears reports 45fps because it is using llvmpipe instead of VC4.
When enabling the GL driver via raspi-config, raspi-config should remove/disable /usr/share/X11/xorg.xonf.d/99-fbturbo.conf (e.g. rename it to disable it), but it does not, which results in Xorg not using the GL driver. A manual workaround is renaming this file manually (don't forget to rename it back when disabling the GL driver or you'll get no video!).
So this is IMO at least a bug in raspi-config.
Why jessie gives 180fps in glxgears even when using llvmpipe, I have no idea. llvmpipe is software rendered, it's not VC4 which is hardware rendered.