Since there is no point in requesting css / images when testing file locks, you can easily use ab (apache bench): http://httpd.apache.org/docs/2.2/programs/ab.html
Note, stat calls are one of the focus points in 4.1, to improve performance on windows / os x / nfs and other clustered file systems.
One patch for 4.x that are awaiting approval might interest you (so you get a idea of how 4.1 will work): http://issues.ez.no/IssueView.php?Id=12137&activeItem=5#comment257136
