Re: Why HZ on i386 is 100 ?

[george anzinger <george@mvista.com>]

Alan Cox wrote:
> 
> > I must not be making my self clear :)  The overhead has nothing to do
> > with hardware.  It is all timer list insertion and deletion.  The
> > problem is that we need to do this at context switch rates, which are
> > MUCH higher that tick rates and, even with the O(1) insertion code,
> > cause the overhead to increase above the ticked overhead.
> 
> I remain unconvinced. Firstly the timer changes do not have to
> occur at schedule rate unless your implementaiton is incredibly naiive.

OK, I'll bite, how do you stop a task at the end of its slice if you
don't set up a timer event for that time?

> Secondly for the specfic schedule case done that way, it would be even more
> naiive to use the standard timer api over a single compare to getthe
> timer list versus schedule clock.

I guess it is my day to be naive :)  What are you suggesting here?

-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Real time sched:  http://sourceforge.net/projects/rtsched/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml