Subject: Re: Why HZ on i386 is 100 ?
To: george@mvista.com (george anzinger)
Date: Sat, 27 Apr 2002 21:26:32 +0100 (BST)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), ak@suse.de (Andi Kleen),
        linux-kernel@vger.kernel.org
In-Reply-To: <3CC713A0.E501AC66@mvista.com> from "george anzinger" at Apr 24, 2002 01:20:48 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

> > 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?

At high scheduling rate you task switch more often than you hit the timer,
so you want to handle it in a lazy manner most of the time. Ie so long as
the timer goes off before the time slice expire why frob it

> > 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?

At the point you think about setting the timer register you do

	next_clock = first_of(timers->head, next_timeslice);
	if(before(next_clock, current_clock)
	{
		current_clock = next_clock;
		set_timeout(next_clock);
	}

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