linux-kernel - Re: [PATCH] [15/58] i386: Rewrite sched

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Date:	Thu, 19 Jul 2007 10:31:56 -0700
From:	Daniel Walker <dwalker@...sta.com>
To:	Andi Kleen <ak@...e.de>
Cc:	patches@...-64.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [15/58] i386: Rewrite sched_clock

On Thu, 2007-07-19 at 19:22 +0200, Andi Kleen wrote:
> On Thursday 19 July 2007 19:15:38 Daniel Walker wrote:
> > On Thu, 2007-07-19 at 19:13 +0200, Andi Kleen wrote:
> > > > What about using the cycles2ns() clocksource helpers, it would eliminate
> > > > the duplication of the shift/multiply math .
> > > 
> > > They are completely different from what clocksource provides.
> > 
> > How so?
> 
> The new sched_clock's works CPU local and relative to the last sync point. 
> 

Right, I guess I'm speaking more low-level than that .. Both function do
shift-multiply style math .. So between the two the cycles to
nanoseconds conversion code is duplicated, and the code to calculate the
multiply value is duplicated ..

>>From my perspective a downside to sched_clock is that the math is
duplicated per architecture .. I think it would be a win to use the
generic functions if it's possible..

Daniel

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