Fwd: Timestamp and Timers Questions

Hello,

I was just wondering if you could answer a few questions about the
implementation of the Click Router.

I'm trying to implement a protocol Element.  The implementation is for
testing and verification of the protocol, so precision and speed are a
factor.  I've been looking at the Click source code for the past few weeks
trying to figure out how precise the Timers and Timestamp are.

Form what I understand, all the Elements that depend on system time rely on
the Timestamp Element.  The timestamp.hh header file has a definition for
different inline assign() functions, but there are many #if statements that
control which macros get defined and I'm not sure how to tell which ones
are actually being used when compiling the code.

Is there a simple way to tell which #if statements are invoked?
This would make it much easier to focus on specific parts of the code.

I would also like to ask how the Timestamp gets the system time.  I saw
that the assign_now() inline function calls current_kernel_time(), but I
wasn't able to trace this call back to its origin.

When running on Linux, does the Click Router use system calls to get the
time (such as POSIX)?

I would also greatly appreciate it if you can offer any extra tips for
understanding the Timestamp implementation.

Thanks for your help.