From: Jesse Barnes <jesse.barnes@intel.com>
To: Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH] trim memory not covered by WB MTRRs
Date: Tue, 12 Jun 2007 08:29:21 -0700
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Cc: Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
       Justin Piszcz <jpiszcz@lucidpixels.com>,
       "Eric W. Biederman" <ebiederm@xmission.com>
References: <200706071530.51552.jesse.barnes@intel.com> <20070612145007.GA5986@ucw.cz>
In-Reply-To: <20070612145007.GA5986@ucw.cz>
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On Tuesday, June 12, 2007 7:50:08 Pavel Machek wrote:
> Hi!
>
> > On some machines, buggy BIOSes don't properly setup WB MTRRs to
> > cover all available RAM, meaning the last few megs (or even gigs)
> > of memory will be marked uncached.  Since Linux tends to allocate
> > from high memory addresses first, this causes the machine to be
> > unusably slow as soon as the kernel starts really using memory
> > (i.e. right around init time).
> >
> > +	if ((highest_addr >> PAGE_SHIFT) != end_pfn) {
> > +		printk(KERN_WARNING "***************\n");
> > +		printk(KERN_WARNING "**** WARNING: likely BIOS bug\n");
> > +		printk(KERN_WARNING "**** MTRRs don't cover all of "
> > +		       "memory, trimmed %ld pages\n", end_pfn -
> > +		       (highest_addr >> PAGE_SHIFT));
> > +		printk(KERN_WARNING "***************\n");
> > +		end_pfn = highest_addr >> PAGE_SHIFT;
>
> Missing 4K of memory is not worth 4K of junk in syslog per boot. Can
> you drop the stars and stop shouting?

How missing about 1G of memory?  We already discussed this, and Andi and 
Venki felt that either a panic or a really obnoxious message was the 
way to go...

Jesse
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