延迟数
type | range | for |
---|---|---|
即时响应 | < 100ms | 搜索自动补全、按钮点击 |
流畅响应 | 100ms - 300ms | 拖拽、滚动、页面、内容加载 |
可接受响应 | 300ms - 1000ms | 交互式应用、提交表单 |
过长响应 | > 1000ms | 用户会感到延迟 |
VoIP | 150ms - 300ms | 语音通话 |
debounce | for |
---|---|
100-200ms | UI元素的交互 - 滑块、拖动 |
200-500ms | 轻量级的用户输入 - 搜索触发请求 |
500-1000ms | 数据密集型的操作 - 实时数据校验 |
Latency Comparison Numbers ~ 2012
- Interactive Latency Numbers Every Programmer Should Know
- HN
- Gist Neo
- Grace Hopper explains Nanoseconds
- Global Ping
- https://computers-are-fast.github.io/
computer latency | nano seconds | micro seconds | milliseconds | relative |
---|---|---|---|---|
L1 cache reference | 0.5 ns | |||
Branch mispredict | 5.0 ns | |||
L2 cache reference | 7.0 ns | 14x L1 cache | ||
Mutex lock/unlock | 25.0 ns | |||
Main memory reference | 100.0 ns | 20x L2 cache, 200x L1 cache | ||
Compress 1K bytes with Zippy | 3,000.0 ns | 3 us | ||
Send 1K bytes over 1 Gbps network | 10,000.0 ns | 10 us | ||
Read 4K randomly from SSD | 150,000.0 ns | 150 us | ~1GB/sec SSD | |
Read 1 MB sequentially from memory | 250,000.0 ns | 250 us | ||
Round trip within same datacenter | 500,000.0 ns | 500 us | 0.5 ms | |
Read 1 MB sequentially from SSD | 1,000,000.0 ns | 1,000 us | 1 ms | ~1GB/sec SSD, 4X memory |
Disk seek | 10,000,000.0 ns | 10,000 us | 10 ms | 20x datacenter roundtrip |
Read 1 MB sequentially from disk | 20,000,000.0 ns | 20,000 us | 20 ms | 80x memory, 20X SSD |
Send packet CA->Netherlands->CA | 150,000,000.0 ns | 150,000 us | 150 ms |
Misc
common latency | ms | s |
---|---|---|
120 fps | 8 ms | 1/120 s |
60 fps | 16 ms | 1/60 s |
24 fps | 41 ms | 1/24 s |
human lantency | ms | s |
---|---|---|
eye blink | 100-150 ms | 0.1-0.5 s |
human reaction time | 250 ms | 0.25 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
unit | stand for | n | mean |
---|---|---|---|
ns | nano second | 10^9 | 纳秒 |
us | micro second | 10^6 | 微秒 |
ms | milli second | 10^3 | 毫秒 |
s | second | 1 | 秒 |
ns | us | ms | s |
---|---|---|---|
1 | 10^-3 | 10^-6 | 10^-9 |
1000 | 1 | 10^-3 | 10^-6 |
10^6 | 1000 | 1 | 10^-3 |
10^9 | 10^6 | 1000 | 1 |
datacenter vs region vs zone vs vs cluster vs rack
- datacenter - dc
- 逻辑机房
- 可能在同一个 region
- 相同 dc 内 < 1ms
- 相同 region 内 < 10ms
- 不同 region 则延时不确定 - 可能跨越半个地球
- 低到 < 10ms
- 高到 > 300ms
- cluster
- 逻辑概念
- 通常在一个 dc
- rack
- 不同服务器最近接近的定义
- 相同交换机背板
- region - 区域 - 由多个地区组成
- 独立地理位置
- zone - 地区
- 故障网域