Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15

[Mark_H_Johnson]

The code does not quite match either pattern but is perhaps
more like your second example.

For reference, the cpu_delay loop looks like this...

  t1 = mygettime();
  for(u=0;u<(loops/1000);u++) {
    t0 = t1;
    if (do_a_trace) {
      gettimeofday(0, (struct timezone*)1);
    }
    for (v=0;v<1000;v++)
      k+=1;
    t1 = mygettime();
    if ((t1-t0)>max_delay){
      delay++;
      if (do_a_trace) {
        gettimeofday(0,0);
        do_a_trace = 0;
        printf("Trace triggered with %f second delay.\n",t1-t0);
      }
    }
  }

I was trying to avoid the extra "rdtsc" overhead (plus the
floating point calculations) so - yes, I could have cases
where the time I measure is not caught by the kernel tracer.

[do some tests...]
Now I'm 5 for 5 with the revised code. Odd that all the numbers
are within about 2 or 3 usec (application measured / kernel measured).
If it was as bad as I was measuring it, I would have expected
one or two to be really off.

  --Mark

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