linux-kernel - Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

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Message-ID: <20071215225943.GE2434@elf.ucw.cz>
Date:	Sat, 15 Dec 2007 23:59:43 +0100
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Rene Herman <rene.herman@...il.com>,
	"David P. Reed" <dpreed@...d.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80
	on some AMD64x2 laptops, etc.

On Fri 2007-12-14 15:23:55, Ingo Molnar wrote:
> 
> * Rene Herman <rene.herman@...il.com> wrote:
> 
> > --- a/init/main.c
> > +++ b/init/main.c
> > @@ -229,10 +229,9 @@ static int __init obsolete_checksetup(char *line)
> >  }
> >
> >  /*
> > - * This should be approx 2 Bo*oMips to start (note initial shift), and will
> > - * still work even if initially too large, it will just take slightly longer
> > + * Initial value roughly corresponds to a 1 GHz CPU
> >   */
> > -unsigned long loops_per_jiffy = (1<<12);
> > +unsigned long loops_per_jiffy = 1000000000 / HZ;
> >
> >  EXPORT_SYMBOL(loops_per_jiffy);
> 
> this is a factor of ~2400 increase - this will take an eternity to boot 
> on any older CPU.

I don't think we are using outb_p before loops_per_jiffy are
initialized -- I believe I'd see oopsen if we did. Factor 2400
increase is bad, but if it only converts 10x 1usec delay into 10x
24msec delay, it is not _that_ bad.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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