计算机硬件操作延时

有空一起学习 2020年2月1日13:01:25 发表评论

文章最后编辑于：2020-2-3 13:06:25

来源：Latency Numbers Every Programmer Should Know。

图片版：

计算机硬件操作延时

文字版：

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

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

中文整理版：

操作	耗时	备注
CPU一级缓存寻址	0.5纳秒
CPU二级缓存寻址	7纳秒
互斥锁	25纳秒
内存寻址	100纳秒
使用zippy压缩1k文件	3000纳秒（3微秒）
在1Gbps的网络中发送1k数据	10000纳秒（10微秒）
从ssd中随机读取4KB数据	150000纳秒（150微秒）	SSD速率：1GB/s
从内存中顺序读取1MB	250000纳秒（250微秒）
同一数据中心往返耗时	500000纳秒（500微秒）
从ssd中随机读取1MB数据	1000000纳秒（1000微秒，1毫秒）	SSD速率：1GB/s
磁盘寻址	10000000纳秒（10000微秒，10毫秒）	约等于20次数据中心往返
从磁盘中顺序读取1MB数据	20000000纳秒（20000微秒，20毫秒）