Can Tang authored Dec 10, 2009 and Nick Mathewson committed Dec 12, 2009

Each circuit is ranked in terms of how many cells from it have been
relayed recently, using a time-weighted average.

This patch has been tested this on a private Tor network on PlanetLab,
and gotten improvements of 12-35% in time it takes to fetch a small
web page while there's a simultaneous large data transfer going on
simultaneously.

[Commit msg by nickm based on mail from Ian Goldberg.]