x86::time

Function rdtscp

Source 
pub unsafe fn rdtscp() -> (u64, u32)
Expand description

Read the time stamp counter.

The RDTSCP instruction waits until all previous instructions have been executed before reading the counter. However, subsequent instructions may begin execution before the read operation is performed.

Volatile is used here because the function may be used to act as an instruction barrier.

§Returns

  • The current time stamp counter value of the CPU as a u64.
  • The contents of IA32_TSC_AUX on that particular core. This is an OS defined value. For example, Linux writes numa_id << 12 | core_id into it. See also crate::rdpid.

§Note

One can use core::arch::x86_64::__rdtscp from the Rust core library as well. We don’t rely on it because it only returns the time-stamp counter of rdtscp and not the contents of IA32_TSC_AUX.

§Safety

  • Causes a GP fault if the TSD flag in register CR4 is set and the CPL is greater than 0.