Re: preempt-timing-2.6.8-rc1

[Nick Piggin]

William Lee Irwin III wrote:
> William Lee Irwin III wrote:
>
> > > +		unsigned long preempt_exit
> > > +				= (unsigned long)__builtin_return_address(0);
> > > +		hold = sched_clock() - __get_cpu_var(preempt_timings) + 
> > > 999999;
> > > +		do_div(hold, 1000000);
> > > +		if (preempt_thresh && hold > preempt_thresh &&
> > > +							printk_ratelimit()) {
>
>
> On Tue, Jul 13, 2004 at 10:51:24PM +1000, Nick Piggin wrote:
>
> > This looks wrong. This means hold times of 1ns to 1000000ns trigger the
> > exceeded 1ms threshold, 1000001 to 2000000 trigger the 2ms one, etc.
> > Removing the + 999999 gives the correct result:
> > 1000000 - 1999999ns triggers the 1ms threshold
> > 2000000 - 2999999ns triggers the 2ms threshold
> > etc
> > Or have I missed something?
>
>
> AFAICT this is nothing more than rounding up.

But you want to round down by definition of preempt_thresh, don't you?

preempt_thresh = 1ms = 1000000us
ie. warn me if the lock hold goes _to or above_ 1000000us
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