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延迟数

  • VoIP 可接受 150ms - 300ms

Latency Comparison Numbers ~ 2012#

computer latencynano secondsmicro secondsmillisecondsrelative
L1 cache reference0.5 ns
Branch mispredict5.0 ns
L2 cache reference7.0 ns14x L1 cache
Mutex lock/unlock25.0 ns
Main memory reference100.0 ns20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy3,000.0 ns3 us
Send 1K bytes over 1 Gbps network10,000.0 ns10 us
Read 4K randomly from SSD150,000.0 ns150 us~1GB/sec SSD
Read 1 MB sequentially from memory250,000.0 ns250 us
Round trip within same datacenter500,000.0 ns500 us0.5 ms
Read 1 MB sequentially from SSD1,000,000.0 ns1,000 us1 ms~1GB/sec SSD, 4X memory
Disk seek10,000,000.0 ns10,000 us10 ms20x datacenter roundtrip
Read 1 MB sequentially from disk20,000,000.0 ns20,000 us20 ms80x memory, 20X SSD
Send packet CA->Netherlands->CA150,000,000.0 ns150,000 us150 ms

Misc#

common latencymss
120 fps8 ms1/120 s
60 fps16 ms1/60 s
24 fps41 ms1/24 s
human lantencymss
eye blink100-150 ms0.1-0.5 s
human reaction time250 ms0.25 s
  • Nerve conduction velocity/神经传导速度 ~ 40m/s
  • 音速 - 343 m/s
  • 光速 - 299,792,458 m / s

Unit#

unitstand fornmean
nsnano second10^9纳秒
usmicro second10^6微秒
msmilli second10^3毫秒
ssecond1
nsusmss
110^-310^-610^-9
1000110^-310^-6
10^61000110^-3
10^910^610001