Re: [2.6.16-mm1 patch] throttling tree patches

[Mike Galbraith <efault@gmx.de>]

On Sat, 2006-03-25 at 11:37 +1100, Peter Williams wrote:
> Mike Galbraith wrote:
> > Greetings,
> > 
> > I've broken down my throttling tree into 6 patches, which I'll send as
> > replies to this start-point.
> > 
> > Patch 1/6
> > 
> > Ignore timewarps caused by SMP timestamp rounding.  Also, don't stamp a
> > task with a computed timestamp, stamp with the already called clock.
> > 
> > Signed-off-by: Mike Galbraith <efault@gmx.de>
> > 
> > --- linux-2.6.16-mm1/kernel/sched.c.org	2006-03-23 15:01:41.000000000 +0100
> > +++ linux-2.6.16-mm1/kernel/sched.c	2006-03-23 15:02:25.000000000 +0100
> > @@ -805,6 +805,16 @@
> >  	unsigned long long __sleep_time = now - p->timestamp;
> >  	unsigned long sleep_time;
> >  
> > +	/*
> > +	 * On SMP systems, a task can go to sleep on one CPU and
> > +	 * wake up on another.  When this happens, the timestamp
> > +	 * is rounded to the nearest tick,
> 
> Is this true?  There's no rounding that I can see.

Instrumenting it looked the same as rounding down, putting now in the
past was the result.

> Of course, that doesn't mean that this chunk of code isn't required just 
> that the comment is misleading.

I'm not attached to the comment.

	-Mike