The correct one for Sierra to turn it on:

sudo nvram boot-args="serverperfmode=1 $(nvram boot-args 2>/dev/null | cut -f 2-)"

And to turn it off:

sudo nvram boot-args="$(nvram boot-args 2>/dev/null | sed -e $'s/boot-args\t//;s/serverperfmode=1//')"

To check if the the performance mode is turned on:

josh@Neptun:~ $ nvram boot-args
boot-args serverperfmode=1

And you need to reboot to make it work!

If you see the following, it is the default:

josh@Neptun:~ $ nvram boot-args
nvram: Error getting variable - 'boot-args': (iokit/common) data was not found

The following will NOT work:

sudo serverinfo —setperfmode 1
sudo serveradmin settings info:enableServerPerformanceMode = yes

More info: Apple