tsc

Get unix time (nanoseconds) in blazing low latency. About 10x~100x faster than time.Now().UnixNano().

• Time Stamp Counter (TSC)

  Based on CPU's TSC register.

• Low Latency

  Under 10ns to get each timestamp.

• Stable

  Unlike time.Now(), the latency of tsc is stable.

  Although time.Now() is using VDSO to get time, but it's unstable, sometimes it will take more than 1000ns.

• High Precision

  tsc's precision is nanosecond.

• Calibrate

  Could be calibrated according to wall clock periodically, no worry about NTP. More details: func Calibrate() in tsc_amd64.go

Performance

Clock Offset

The offset between wall clock and tsc is extremely low (under dozens ns in avg, maximum is hundreds-1000 ns), see test codes for more details.

Warning

If you need really accurate clock, you should run gofreq first to get TSC frequency, then set the value to Frequency Table.

Limitation

• Intel Only

  Only tested on Intel platform.

• Invariant TSC supports

  Invariant TSC could make sure TSC got synced among multi CPUs. They will be reset at same time, and run in same frequency.

• Reliable TSC frequency

  The TSC frequency provided by Intel CPU must be accurate.

• AVX supports

  Some instructions need AVX, see tsc_amd64.s for details.

• No support on virtual machine

  Have tested on AWS EC2, because of CPUID.15H is disabled. And tsc may won't work as we expect on a virtual machine.

• Handle Limitation

  If tsc can't be enabled, it will use time.Now().UnixNano() automatically.