On Sun, Sep 2, 2012 at 7:56 PM, Kazu Yamamoto <kazu@iij.ad.jp> wrote:
To my experience, the assumption 2) is not right. getttimeofday()
is implemented in user land in Linux 3 but it is a system call
in Linux 2.

Just a nit: your history here is not correct. gettimeofday has been implemented as a vsyscall for a long time, maybe 5 years. And while it's faster than int 0x80, it's not that much faster: 2x or so on modern hardware.