[wahern]

The gettimeofday vDSO does use the TSC. The purpose of the vDSO is making visible the continuously updated values necessary for userland to adjust and correct TSC-based calculations. Many of those values are still necessary even when the TSC is shared and constant-rate.

A pure TSC implementation will sacrifice accuracy (because it's not being trained by the HPET or corrected by NTP), performance (because it'll need to do a full syscall occasionally), or both.

If you're sophisticated like NetFlix you can probably assure yourself it's no big deal. But it's a bad idea for others to blindly do the same thing. Look at the issue with Go's timeouts. Go used gettimeofday rather than CLOCK_MONOTONIC because the authors assumed the behavior of Google's system's clock skewing algorithm. That assumption broke spectacularly for many other people not using Google's servers.