lkml.org 
[lkml]   [2007]   [Sep]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: MTRR initialization
    Date
    On Wednesday, September 19, 2007 11:50:23 pm Andi Kleen wrote:
    > Jesse Barnes <jesse.barnes@intel.com> writes:
    > > To do this in a nicer way (and be less vulnerable to similar BIOS
    > > funkiness) the kernel really needs full PAT support. That should allow
    > > WC over WB and WC over UC mappings to occur, at least if I'm
    > > remembering the docs right...
    >
    > PAT only really helps for device driver performance optimizations.
    > But if the basic WB MTRRs are wrong PAT cannot really salvage it.

    Look at the original bug report. There's a bug WB region so any subsequent WC
    mappings via the MTRRs won't work, so you need PAT to do WC (unless you want
    to rewrite all your MTRR settings as Howard has to do now).

    Seems like more and more machines are being setup this way, and until we have
    PAT users will have to jump through hoops to get good performance.

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

    \
     
     \ /
      Last update: 2007-09-20 17:13    [W:0.023 / U:1.092 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site