The baseline is static: low QoS tasks are dispatched to the E cores, while high QoS tasks are dispatched to P cores. IIRC high QoS cores can migrate to the E cores if all P cores are loaded, but my understanding is that the lowest QoS tasks (background) never get promoted to P cores.

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drob518 10 hours ago | parent [-]

How is the QoS communicated to the scheduler? Is there a mark on the binary or does the code do it at thread startup?

	▲	dcrazy 10 hours ago \| parent \| next [-]
		The Apple software stack makes heavy use of thread pools via libdispatch. Individual work items are tagged with QoS, which influences which thread picks up the work item from the queue.
	▲	saagarjha 10 hours ago \| parent \| prev [-]
		It’s done in code.