Re: [PATCH 3/5] lockstat: core infrastructure

[Daniel Walker <dwalker@mvista.com>]

On Fri, 2007-06-01 at 15:12 +0200, Ingo Molnar wrote:
> * Daniel Walker <dwalker@mvista.com> wrote:
> 
> > On Wed, 2007-05-30 at 19:16 +0200, Peter Zijlstra wrote:
> 
> > > I think you are mistaken here; the two are similar but not 
> > > identical.
> > > 
> > > I see sched_clock() as fast first, accurate second. Whereas the 
> > > clocksource thing is accurate first, fast second.
> > 
> > This is true .. However, if there is a speed different it's small.
> 
> Ugh. Have you ever compared pmtimer (or even hpet) against TSC based 
> sched_clock()? What you write is so wrong that it's not even funny. You 
> keep repeating this nonsense despite having been told multiple times 
> that you are dead wrong.

Yes I have, and your right there is a difference, and a big
difference .. Above I was referring only to the TSC clocksource, since
that's an apples to apples comparison .. I would never compare the TSC
to the acpi_pm, that's no contest ..

The acpi_pm as sched_clock() with hackbench was about %25 slower, the
pit was 10x slower approximately. (I did this months ago.)

Daniel