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: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
