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    Subject[tip:sched/urgent] sched/numa: Add SD_PERFER_SIBLING to CPU domain
    Commit-ID:  6956dc568f34107f1d02b24f87efe7250803fc87
    Gitweb: http://git.kernel.org/tip/6956dc568f34107f1d02b24f87efe7250803fc87
    Author: Alex Shi <alex.shi@intel.com>
    AuthorDate: Fri, 20 Jul 2012 14:19:50 +0800
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Thu, 26 Jul 2012 11:46:58 +0200

    sched/numa: Add SD_PERFER_SIBLING to CPU domain

    Commit 8e7fbcbc22c ("sched: Remove stale power aware scheduling remnants
    and dysfunctional knobs") removed SD_PERFER_SIBLING from the CPU domain.

    On NUMA machines this causes that load_balance() doesn't perfer LCPU in
    same physical CPU package.

    It causes some actual performance regressions on our NUMA machines from
    Core2 to NHM and SNB.

    Adding this domain flag again recovers the performance drop.

    This change doesn't have any bad impact on any of my benchmarks:
    specjbb, kbuild, fio, hackbench .. etc, on all my machines.

    Signed-off-by: Alex Shi <alex.shi@intel.com>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Link: http://lkml.kernel.org/r/1342765190-21540-1-git-send-email-alex.shi@intel.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    include/linux/topology.h | 1 +
    1 files changed, 1 insertions(+), 0 deletions(-)

    diff --git a/include/linux/topology.h b/include/linux/topology.h
    index e91cd43..fec12d6 100644
    --- a/include/linux/topology.h
    +++ b/include/linux/topology.h
    @@ -164,6 +164,7 @@ int arch_update_cpu_topology(void);
    | 0*SD_SHARE_CPUPOWER \
    | 0*SD_SHARE_PKG_RESOURCES \
    | 0*SD_SERIALIZE \
    + | 1*SD_PREFER_SIBLING \
    , \
    .last_balance = jiffies, \
    .balance_interval = 1, \

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