Re: [PATCH] trim memory not covered by WB MTRRs
- From: Pavel Machek <pavel@xxxxxx>
- Date: Tue, 12 Jun 2007 23:30:20 +0200
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...
Just use panic, then.
Pavel,
who still thinks anyone missing 1GB of ram will not miss
friendly notice in dmesg, even if it goes without 20 stars.
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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