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

treyharris

Why the ident attribute doesn't work in Git like in CVS or SVN

This is a wrinkle that people often don't get about the ident attribute: in CVS or Subversion, it would be legitimate to have a VERSION file containing nothing but $Id$ as a way of tracking that the right push had happened; if you did that with git, you'd get nothing useful. If you run the script below (or just read it and the output that follows), you can see why.

(Please direct comments on this to https://plus.google.com/+TreyHarris/posts/KRgNG3zDk9x.)

How do you do it?

Setting it up in Git is relatively simple. You create (or edit) the file .gitattributes and add a line telling Git to replace $Id$ when found in files that match certain filenames: