Hello there,

I wish to determine at the WIFI card driver-level exactly
at what point in time a given packet is queued up for transmission with a precision of nanoseconds. In order to determine the instantaneous time, what is the best tool available as I do not think that I can use gettimeofday() at the kernel level as it requires sys/time.h. Do you think jiffies can be used but I am not sure about its precision.

Please shed some light on this as early as you can.

Thanks in advance for taking your invaluable time to answer my question.

Cheers

Siva

You're not going to get nanoseconds, no matter what you do, because you do not have a real-time clock with that kind of precision.

"Jiffies" are the resolution of the system heartbeat-interrupt clock. The current x86 processors offer an instruction that will store a clock-value that basically increments with each CPU clock-cycle. There are macros in the kernel source-code that can issue it.

But... what are you trying to do? Easily the best way of analyzing this sort of thing is basically ex post facto, from some kind of log analysis.

I think jiffies is suffice, as after having a careful look at the way IEEE 802.11 works, I came to a conclusion that precision in the order of milli/micro seconds is enough.

Thanks for you commnts.