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    Subject[RFC PATCH v5 6/7] sched: add SD_BALANCE_NEWIDLE at MC and CPU level for sched_mc>0
    Date
    Add SD_BALANCE_NEWIDLE flag at MC level and CPU level
    if sched_mc is set. This helps power savings and
    will not affect performance when sched_mc=0

    Ingo and Mike Galbraith have optimised the SD flags by
    removing SD_BALANCE_NEWIDLE at MC and CPU level. This
    helps performance but hurts power savings since this
    slows down task consolidation by reducing the number
    of times load_balance is run.

    sched: fine-tune SD_MC_INIT
    commit 14800984706bf6936bbec5187f736e928be5c218
    Author: Mike Galbraith <efault@gmx.de>
    Date: Fri Nov 7 15:26:50 2008 +0100

    sched: re-tune balancing -- revert
    commit 9fcd18c9e63e325dbd2b4c726623f760788d5aa8
    Author: Ingo Molnar <mingo@elte.hu>
    Date: Wed Nov 5 16:52:08 2008 +0100

    This patch selectively enables SD_BALANCE_NEWIDLE flag
    only when sched_mc is set to 1 or 2. This helps power savings
    by task consolidation and also does not hurt performance at
    sched_mc=0 where all power saving optimisations are turned off.

    Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
    ---

    include/linux/sched.h | 10 ++++++++++
    include/linux/topology.h | 6 ++++--
    2 files changed, 14 insertions(+), 2 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 888f2b2..e894892 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -782,6 +782,16 @@ enum powersavings_balance_level {
    ((sched_mc_power_savings || sched_smt_power_savings) ? \
    SD_POWERSAVINGS_BALANCE : 0)

    +/*
    + * Optimise SD flags for power savings:
    + * SD_BALANCE_NEWIDLE helps agressive task consolidation and power savings.
    + * Keep default SD flags if sched_{smt,mc}_power_saving=0
    + */
    +
    +#define POWERSAVING_SD_FLAGS \
    + ((sched_mc_power_savings || sched_smt_power_savings) ? \
    + SD_BALANCE_NEWIDLE : 0)
    +
    #define test_sd_parent(sd, flag) ((sd->parent && \
    (sd->parent->flags & flag)) ? 1 : 0)

    diff --git a/include/linux/topology.h b/include/linux/topology.h
    index 117f1b7..26c608c 100644
    --- a/include/linux/topology.h
    +++ b/include/linux/topology.h
    @@ -125,7 +125,8 @@ void arch_update_cpu_topology(void);
    | SD_WAKE_AFFINE \
    | SD_WAKE_BALANCE \
    | SD_SHARE_PKG_RESOURCES\
    - | BALANCE_FOR_MC_POWER, \
    + | BALANCE_FOR_MC_POWER \
    + | POWERSAVING_SD_FLAGS, \
    .last_balance = jiffies, \
    .balance_interval = 1, \
    }
    @@ -150,7 +151,8 @@ void arch_update_cpu_topology(void);
    | SD_BALANCE_FORK \
    | SD_WAKE_AFFINE \
    | SD_WAKE_BALANCE \
    - | BALANCE_FOR_PKG_POWER,\
    + | BALANCE_FOR_PKG_POWER \
    + | POWERSAVING_SD_FLAGS, \
    .last_balance = jiffies, \
    .balance_interval = 1, \
    }


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