Commit 100fdaee authored Dec 18, 2008 by Vaidyanathan Srinivasan Committed by Ingo Molnar Dec 19, 2008

sched: add SD_BALANCE_NEWIDLE at MC and CPU level for sched_mc>0



Impact: change task balancing to save power more agressively

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 14800984
        Author: Mike Galbraith <efault@gmx.de>
        Date:   Fri Nov 7 15:26:50 2008 +0100

    sched: re-tune balancing -- revert
        commit 9fcd18c9
        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>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent ad273b32

include/linux/sched.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -792,6 +792,19 @@ static inline int sd_balance_for_package_power(void)
		return 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
		*/

		static inline int sd_power_saving_flags(void)
		{
		if (sched_mc_power_savings \| sched_smt_power_savings)
		return SD_BALANCE_NEWIDLE;

		return 0;
		}

		struct sched_group {
		struct sched_group next; / Must be a circular list */

include/linux/topology.h

+4 −2

Original line number	Diff line number	Diff line
		@@ -125,7 +125,8 @@ int arch_update_cpu_topology(void);
		\| SD_WAKE_AFFINE \
		\| SD_WAKE_BALANCE \
		\| SD_SHARE_PKG_RESOURCES\
		\| sd_balance_for_mc_power(),\
		\| sd_balance_for_mc_power()\
		\| sd_power_saving_flags(),\
		.last_balance = jiffies, \
		.balance_interval = 1, \
		}
		@@ -150,7 +151,8 @@ int arch_update_cpu_topology(void);
		\| SD_BALANCE_FORK \
		\| SD_WAKE_AFFINE \
		\| SD_WAKE_BALANCE \
		\| sd_balance_for_package_power(),\
		\| sd_balance_for_package_power()\
		\| sd_power_saving_flags(),\
		.last_balance = jiffies, \
		.balance_interval = 1, \
		}

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