On Wed, 6 Jun 2007 12:29:23 -0700 Jesse Barnes <[EMAIL PROTECTED]> 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. i386 allmodconfig: arch/i386/kernel/cpu/mtrr/main.c: In function 'mtrr_trim_uncached_memory': arch/i386/kernel/cpu/mtrr/main.c:655: error: 'end_pfn' undeclared (first use in this function) arch/i386/kernel/cpu/mtrr/main.c:655: error: (Each undeclared identifier is reported only once arch/i386/kernel/cpu/mtrr/main.c:655: error: for each function it appears in.) I'll poke some ifdefs in there. - 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/