计算机延迟比较

Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference                           0.5 ns
	Branch mispredict                            5   ns
	L2 cache reference                           7   ns                      14x L1 cache
	Mutex lock/unlock                           25   ns
	Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy             3,000   ns        3 us
	Send 1K bytes over 1 Gbps network       10,000   ns       10 us
	Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD
	Read 1 MB sequentially from memory     250,000   ns      250 us
	Round trip within same datacenter      500,000   ns      500 us
	Read 1 MB sequentially from SSD*     1,000,000   ns    1,000 us    1 ms  ~1GB/sec SSD, 4X memory
	Disk seek                           10,000,000   ns   10,000 us   10 ms  20x datacenter roundtrip
	Read 1 MB sequentially from disk    20,000,000   ns   20,000 us   20 ms  80x memory, 20X SSD
	Send packet CA->Netherlands->CA    150,000,000   ns  150,000 us  150 ms
	
	Notes
	-----
	1 ns = 10^-9 seconds
	1 us = 10^-6 seconds = 1,000 ns
	1 ms = 10^-3 seconds = 1,000 us = 1,000,000 ns

https://gist.github.com/jboner/2841832

https://computers-are-fast.github.io/