Measuring CPU load

[Mike]

Hi!

It's not really D related, I know, but I don't know where else to ask.

So: I've got this little class that measures in/out time of threads with  
the rdtsc assembler opcode. The relevant thread gets started periodically,  
takes time of start in[t] at the entry point and time of exit out [t] with  
"scope (exit) ...".

This gives me the following measurments:

in[t]   // thread entered (current iteration)
out[t]  // thread exited (current iteration)
in[t-1] // thread entered (last iteration)

And the following formula:

cpuload = 100 * (out[t] - in[t]) / (in[t] - in[t-1]);

to get the cpu load in %.

Now I've tested this and I'm not quite sure. The results are at least  
somewhat  reasonable, although they seem to be double the real value (I've  
got a dual core system) so that might explain that.

But before guessing around I thought I'll ask here if this way of  
measuring is completely wrong or if there's a better way to do that.

-Mike

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