Last active
September 25, 2023 18:20
-
Star 5,000+
You must be signed in to star a gist -
Fork 2,074
You must be signed in to fork a gist
Star
You must be signed in to star a gist
Latency Numbers Every Programmer Should Know
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
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 | |
Credit | |
------ | |
By Jeff Dean: http://research.google.com/people/jeff/ | |
Originally by Peter Norvig: http://norvig.com/21-days.html#answers | |
Contributions | |
------------- | |
'Humanized' comparison: https://gist.github.com/hellerbarde/2843375 | |
Visual comparison chart: http://i.imgur.com/k0t1e.png |
Thanks for sharing your updates.
You could consider adding a context switch for threads right under disk seek:
computer context switches: 1e7 ns
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
this seems misleading, since in common networking terminology 1 Gbps refers to throughput ("size of the pipe"), but this list is about "latency," which is generally independent of throughput - it takes the same amount of time to send 1K bytes over a 1 Mbps network and a 1 Gbps network
A better description of this measure sounds like "bit rate," or more specifically the "data signaling rate" (DSR) over some communications medium (like fiber). This also avoids the ambiguity of "over" the network (how much distance?) because DSR measures "aggregate rate at which data passes a point" instead of a segment.
Using this definition (which I just learned a minute ago), perhaps a better label would be:
🤷 (also, I didn't check if the math is consistent with this labeling, but I did pull "fiber channel" from the table on the DSR wiki page)