linux-kernel - Re: bcm33xx port

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Message-ID: <Pine.LNX.4.64.0806090839100.25145@anakin>
Date:	Mon, 9 Jun 2008 08:40:57 +0200 (CEST)
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Luke -Jr <luke@...hjr.org>
cc:	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mips@...ux-mips.org
Subject: Re: bcm33xx port

On Sun, 8 Jun 2008, Luke -Jr wrote:
> On Sunday 08 June 2008, Maciej W. Rozycki wrote:
> > On Sun, 8 Jun 2008, Luke -Jr wrote:
> > > >  Not exactly.  Try harder -- this is simple arithmetic and you've got
> > > > all the data given above already. :)
> > >
> > > 200 / 2? I'm not really sure what a 'jiffy' is..
> >
> >  Hmm, I have thought it can be inferred from the code involved or failing
> > that -- Google...  Well, anyway, a jiffy is a tick of the kernel timer or,
> > specifically in this context and to be more precise, the interval between
> > such two consecutive ticks or, in other words, 1/HZ.
                                                     ^^
Look at CONFIG_HZ, which is probably 100, 250, or 1000.

> jiffy = 1 / 200000 HZ = 0.000005 sec/tick
> loop = 200000 instructions / 2 instructions per loop = 100000 loops/sec
> 
> So 0.00000000005 loops per jiffy? But it can't be, since loops_per_jiffy isn't 
> floating point... :/

So loops_per_jiffie is approx. CPU clock frequency / CONFIG_HZ.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds
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