You could also try to set soft affinity with Qubes Admin Events
After setting service and restart all qubes, by default every qube will have soft affinity set to e-cores (will prefer e-cores) except for qubes with tag performance which you set and forget like that (in dom0 terminal):
qvm-tags app-YouTube add performance
and those qubes will have soft affinity (scheduler preference) set to p-cores
It’s also good to set scheduler wieght of dom0 2x as much as other qubes.
Default weight of sched-credit2 for all qubes is 256
xl sched-credit2
here you see, thad dom0 is ID is 0 and by standard all qubes have weight 256, so set it to 512 for dom0:
xl sched-credit2 -d 0 -w 512
PS: weight for sched-credit2 for dom0 is set persistently if you add this command to /etc/rc.d/rc.local