gubatron

DHT Walkthrough Notes

I've put together these notes as I read about DHT's in depth and then learned how the libtorrent implementation based on the Kademlia paper actually works.

What problem does this solve?

400,000,000,000 (400 billion stars), that's a 4 followed by 11 zeros. The number of atoms in the universe is estimated to be around 10^82. A DHT with keys of 160 bits, can have 2^160 possible numbers, which is around 10^48

piscisaureus

Locate the section for your github remote in the .git/config file. It looks like this:

[remote "origin"]
	fetch = +refs/heads/*:refs/remotes/origin/*
	url = git@github.com:joyent/node.git

Now add the line fetch = +refs/pull/*/head:refs/remotes/origin/pr/* to this section. Obviously, change the github url to match your project's URL. It ends up looking like this:

jboner

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