Messages in this thread | | | Date | Wed, 6 Jun 2007 16:26:59 -0400 (EDT) | From | Justin Piszcz <> | Subject | Re: [PATCH] trim memory not covered by WB MTRRs |
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On Wed, 6 Jun 2007, Jesse Barnes wrote:
> 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). > > This patch works around the problem by scanning the MTRRs at > boot and figuring out whether the current end_pfn value (setup > by early e820 code) goes beyond the highest WB MTRR range, and > if so, trimming it to match. A fairly obnoxious KERN_WARNING > is printed too, letting the user know that not all of their > memory is available due to a likely BIOS bug. > > Something similar could be done on i386 if needed, but the boot > ordering would be slightly different, since the MTRR code on i386 > depends on the boot_cpu_data structure being setup. > > Justin, can you please test and make sure this patch works for > you too? It'll only work around the problem, but it's better > than having to do mem= by hand or waiting for a fix from your > BIOS vendor. > > Thanks, > Jesse
Against what kernel version does this patch apply?
linux-2.6.21# patch -p1 < ../mtrr.patch patching file arch/i386/kernel/cpu/mtrr/generic.c Hunk #2 succeeded at 66 (offset -18 lines). patching file arch/i386/kernel/cpu/mtrr/if.c patching file arch/i386/kernel/cpu/mtrr/main.c patching file arch/i386/kernel/cpu/mtrr/mtrr.h can't find file to patch at input line 160 Perhaps you used the wrong -p or --strip option? The text leading up to this was: -------------------------- |diff --git a/arch/x86_64/kernel/bugs.c b/arch/x86_64/kernel/bugs.c |index c3c6b91..c138eac 100644 |--- a/arch/x86_64/kernel/bugs.c |+++ b/arch/x86_64/kernel/bugs.c -------------------------- File to patch:
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