You need to know exactly what you are doing for using rdtsc. There are some external factors that affect the counting such as dynamic clock, and out of order execution. I'm not sure that rdtsc registers are synchronized on different CPUs. Some code for you to play with: https://github.com/petersenna/rdtscbench https://github.com/petersenna/Kernel/tree/master/stopwatch On Mon, Apr 7, 2014 at 3:21 PM, Sunny <sundarcs@gwu.edu> wrote:

Hi all,

I'm running xen 4.2 on Linux Kernel 3.7 and I'm trying to figure out the time taken(latency) by a network packet to reach it's destination VM from the time it arrives at the NIC. What do you think is the best way to do it? I was thinking may be add rdtsc timestamp to the IP options header on arrival, and one more when it reaches to its desired VM and examine the two timestamps. I've not figured out a way to do this yet--but do you think this is a viable option or what other methods would you recommend?

Thanks, Sunny _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

-- Peter