Lots of us have dual graphics cards in the laptops these days, but almost everyone I know tends to use one or the other, hardly ever switching on the fly, since typical usage patterns tend to stick for periods of time.
One thing that almost no one seems to do however is turn off the unusued gpu – when on the move, this can have a significant impact on your battery life.
On CentOS Linux 7, the way to do this would be something like this :
echo ‘OFF’ > /sys/kernel/debug/vgaswitcheroo/switch
And thats it, lterally send it the OFF and the unused gpu is powered down.
You can also querry the interface as follows:
# cat /sys/kernel/debug/vgaswitcheroo/switch
On my Thinkpad T460p it looks like this :
For more info on the vgaswitcheroo, take a look at your kernel document eg https://www.kernel.org/doc/html/v4.10/gpu/vga-switcheroo.html