nice					each process has a niceness
batch job managers	few if any interrupts

Threads are easier than process
	Thread: program registers, PC, flags
	Process: all of that, and MMU, permissions, ...

Hyperthreading, virtual cores
	1 core will have 2 copies of all registers, can run 2 threads in parallel
	
	means: OS knows thread ≠ process

--------------------------------------------------
2 threads access same memory
	2 identical threads, both run 1-assembly instruction function:
		addq $1, (%rax)
	
			assume both share %rax = 0x12340000
			assume before either thread runs, (%rax) = 0
	a. 2			40%
	b. 1			60%
	c. 0			0
	d. 3			0
	e. other		3
	f. depends; could be 1 or 2; depends on runtime randomness
	g. depends; 2 if done one after the other, 1 otherwise

	1	1	0	0	0	0
Core1	L1
			L2	L3	L4	RAM
Core2	L1
	1	1	1

Atomicity			Atomic = cannot be divided


	1	1	0	0	0	0
Core1T1	L1	L2	L3	L4	RAM
Core1T2
	1	1

Race conditions



after a process ends, it is still there: it is a zombie