Re: No 100 HZ timer !

[george anzinger <george@mvista.com>]

"Richard B. Johnson" wrote:
> 
> > george anzinger wrote:
> >
> > > The testing I have done seems to indicate a lower overhead on a lightly
> > > loaded system, about the same overhead with some load, and much more
> > > overhead with a heavy load.  To me this seems like the wrong thing to
> >
> 
> Doesn't the "tick-less" system presume that somebody, somewhere, will
> be sleeping sometime during the 1/HZ interval so that the scheduler
> gets control?
> 
> If everybody's doing:
> 
>         for(;;)
>           number_crunch();
> 
> And no I/O is pending, how does the jiffy count get bumped?

Who cares if it gets bumped?  In the tick less system the jiffy counter
is a function.  Thus, if you need it, it will be current, more current
than in the ticked system because it is calculated on the spot and does
not rely on an interrupt to "bump" it.
> 
> I think the "tick-less" system relies upon a side-effect of
> interactive use that can't be relied upon for design criteria.
> 
Look at the code.  You will find it here:
http://sourceforge.net/projects/high-res-timers

George