Alfonso Acosta 2opremio

macOS Internals

Understand your Mac and iPhone more deeply by tracing the evolution of Mac OS X from prelease to Swift. John Siracusa delivers the details.

Starting Points

How to use this gist

You've got two main options:

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

	roomrate
	========
	{
	'city': 'Berlin',
	'hotel': 'Hilton',
	'date': '2013-08-09'
	'room_type': 'single',
	'occupancy': 2,
	'avail_count': 13,
	'booked_count': 4,

	# put this to your $HOME/.bashrc
	# so you can safely use screen or tmux while preserving ssh-agent forwarding features
	# of your ssh sessions
	test "${SSH_AUTH_SOCK:-}" && test $SSH_AUTH_SOCK != $HOME/.ssh_auth_sock && {
	test -L $HOME/.ssh_auth_sock && \
	test "$(readlink $HOME/.ssh_auth_sock)" = $SSH_AUTH_SOCK \|\| \
	ln -sf $SSH_AUTH_SOCK $HOME/.ssh_auth_sock
	export SSH_AUTH_SOCK=$HOME/.ssh_auth_sock
	}