常见的硬件延迟

Latency Numbers Every Programmer Should Know · GitHub

Latency Comparison Numbers (~2012)
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一级缓存 L1 cache reference                    0.5 ns
分支预测失误 Branch mispredict                5   ns
二级缓存L2 cache reference                      7   ns            14x L1 cache
Mutex lock/unlock                                     25   ns
主内存Main memory reference               100   ns            20x L2 cache, 200x L1 cache
压缩 Compress 1K bytes with Zipp      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 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
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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

下面的有每年的数据

Numbers Every Programmer Should Know By YearNumbers Every Programmer Should Know By YearNumbers Every Programmer Should Know By Year

 一级缓存        1ns

分支预测失败  3ns

二级缓存         4ns

Mutex lock/unlock 17ns

主内存            100ns

Zipp 压缩1k    2,000 ns   

公共网络发2k    44ns  (网络提升很大，不知数据有没问题，发收加起来的话呢)

内存连续读1m 数据 3,000ns

SSD 随机读   16,000ns