Apparently kernel 2.4 gave priority to software interrupts (signals)  so
that itimer() periods are more accurate...(someone please explain)

The net result is that soft real time periodic jobs are now more
accurate.
Using this:

kernel compiled for 1000 timeslices/sec
signal(SIGALRM, handler_func)
setitimer(ITIMER_REAL, &interval, 0)
sched_setscheduler(THIS_PROC, SCHED_FIFO, &my_sched)

We get periods of _fractions_ of milliseconds on k2.4.4 ,  
Whereas on k2.2.17, periods were in multiples of 1 millisecond.

I have an application which uses the above to request alarm handlers at
60 Hz (a 16.66 msec period). On k2.2.17-rtl3.0pre9 the period of the
handler (seen on an oscilloscope) was 17 msec. On k2.4.4-rtl3.1pre3 the
period of the handler is 16.6 msec.

(I'm assuming its the kernel doing this, and not the standard rtlinux
patch.)

-- Steve Rosenbluth

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