On my Windows VirtualBox machine, getElapsedTimeMillis() shows that 640ms pass during a wall clock period of 1000ms. This is rather inaccurate, and this is because we are estimating the select() period on Windows using hardcoded values.

This causes problems for code trying to measure long periods of time with this. For example, mongos cursor timeout code is hoping to time out cursors after ten minutes; instead, on Windows, it will time out in 15.6 minutes (this was causing a unit test failure on Windows).