I am sending network packets from one thread and receiving replies on a 2nd thread that runs on a different CPU core. My process measures the time between send & receive of each packet (similar to ping). I am using rdtsc for getting high-resolution, low-overhead timing, which is needed by my implementation.

All measurments looks reliable. Still, I am worried about rdtsc accuracy across cores, since I've been reading some texts which implied that tsc is not synced between cores.

I found the following info about TSC in wikipedia

Constant TSC behavior ensures that the duration of each clock tick is uniform and supports the use of the TSC as a wall clock timer even if the processor core changes frequency. This is the architectural behavior moving forward for all Intel processors.

Still I am worried about accruracy across cores, and this is my question

More Info

• I run my process on an Intel nehalem machine.
• Operating System is Linux.
• The "constant_tsc" cpu flag is set for all the cores.