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Commit a52bfd73 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Add smt_gain 



The idea is that multi-threading a core yields more work
capacity than a single thread, provide a way to express a
static gain for threads.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: default avatarGautham R Shenoy <ego@in.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
LKML-Reference: <20090901083826.073345955@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent cc9fba7d

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -921,6 +921,7 @@ struct sched_domain { 
	unsigned int newidle_idx;

	unsigned int wake_idx;

	unsigned int forkexec_idx;

	unsigned int smt_gain;

	int flags;			/* See SD_* */

	enum sched_domain_level level;

include/linux/topology.h

+1 −0
Original line number Diff line number Diff line
@@ -99,6 +99,7 @@ int arch_update_cpu_topology(void); 
				| SD_SHARE_CPUPOWER,	\

	.last_balance		= jiffies,		\

	.balance_interval	= 1,			\

	.smt_gain		= 1178,	/* 15% */	\

}

#endif

#endif /* CONFIG_SCHED_SMT */

kernel/sched.c

+7 −1
Original line number Diff line number Diff line
@@ -8523,9 +8523,15 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd) 
		weight = cpumask_weight(sched_domain_span(sd));

		/*

		 * SMT siblings share the power of a single core.

		 * Usually multiple threads get a better yield out of

		 * that one core than a single thread would have,

		 * reflect that in sd->smt_gain.

		 */

		if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1)

		if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {

			power *= sd->smt_gain;

			power /= weight;

			power >>= SCHED_LOAD_SHIFT;

		}

		sg_inc_cpu_power(sd->groups, power);

		return;

	}