I am also experiencing severe performance issues with PHP apps on Docker For Mac.
It seems to be a Volume performance issue as I find I can get a >tenfold increase in performance if I move my Composer vendor directory (which is where all of the libs and their deps live) out of the the shared Volume and into /tmp inside the container. This is far from ideal however, as we may need to make changes to our own libs while they are in place and can no longer do that if they’re not shared. And it confuses the IDE.
I’m using the standard PHP 7 w/ apache Docker image from the hub.
I am also seeing huge CPU spikes when making a request to the web server.
FWIW, I think this is very likely related to File access in mounted volumes extremely slow, CPU bound in my case at least