On Thursday, June 21, 2007 12:40:58 Yinghai Lu wrote: > On 6/7/07, 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. > > > > This patch incorporates the feedback from Eric and Andi: > > - use MAX_VAR_RANGES instead of NUM_VAR_RANGES > > - move array declaration to header file as an extern > > - add command line disable option "disable_mtrr_trim" > > - don't run the trim code if the MTRR default type is cacheable > > - don't run the trim code on non-Intel machines > > > > Justin, feel free to test again if you have time and add your > > "Tested-by" signoff. > > > > Andi, as for large pages, do you think this is ok as is, or should > > I trim a larger granularity? If so, what granularity? > > > > Signed-off-by: Jesse Barnes <[EMAIL PROTECTED]> > > > > Thanks, > > Jesse > > NAK. > > for AMD Rev F Opteron later CPU, BIOS will not set WB in MTRR for 4G > above mem. > > This patch will get rid of those RAM.
Yeah, Eric already mentioned that. I'll rework it to only run on Intel CPUs per Eric's last mail. Thanks, Jesse - 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/
