If anyone wants to do any fun OS X GPU rabbitholing, this command will dump out a bunch of stuff from the IO Registry as an XML/plist:
ioreg -c IOGraphicsAccelerator2 -r -l -a
The PerformanceStatistics and IOReportChannels dicts are particularly juicy, and under IORegistryEntryChildren you can see which processes (IOUserClientCreator) are using what OS-level GPU resources, including Metal vs OpenGL API.
ioreg -c IOGraphicsAccelerator2 -r -l -a
The PerformanceStatistics and IOReportChannels dicts are particularly juicy, and under IORegistryEntryChildren you can see which processes (IOUserClientCreator) are using what OS-level GPU resources, including Metal vs OpenGL API.