Comment 81 for bug 1386721

Experienced this issue on a Dell XPS 15(9530)
intel HD4400 chipset with optimus and an nvidia GT750M card

lsmod shows that after enabling the additional drivers for nvidia, both intel and nvidia modules are loaded. Below is some selected lines from lsmod output:

i2c_algo_bit 13406 1 i915
drm_kms_helper 61627 1 i915
drm 310919 6 i915,drm_kms_helper,nvidia
video 20128 1 i915

According to one askubuntu entry (http://askubuntu.com/questions/128433/how-to-prevent-nvidia-kernel-module-from-loading-ubuntu-12-04-64-bit) bumblebee acts by blacklisting the nvidia module and only having it load for certain display contexts (the windows you want to be accelerated). Seemingly this was in 2012, but i think it probably holds true today

So by simply installing the available bumblebee package (in my case i ticked enable nvidia proprietary driver support in the software center) and rebooting, all performance issues were solved.