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: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Andreas Herrmann <andreas.herrmann3@amd.com> Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com> Acked-by: Gautham R Shenoy <ego@in.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> LKML-Reference: <20090901083826.073345955@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -921,6 +921,7 @@ struct sched_domain {
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unsigned int newidle_idx;
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unsigned int wake_idx;
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unsigned int forkexec_idx;
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unsigned int smt_gain;
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int flags; /* See SD_* */
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enum sched_domain_level level;
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@ -99,6 +99,7 @@ int arch_update_cpu_topology(void);
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| SD_SHARE_CPUPOWER, \
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.last_balance = jiffies, \
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.balance_interval = 1, \
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.smt_gain = 1178, /* 15% */ \
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}
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#endif
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#endif /* CONFIG_SCHED_SMT */
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@ -8523,9 +8523,15 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd)
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weight = cpumask_weight(sched_domain_span(sd));
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/*
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* SMT siblings share the power of a single core.
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* Usually multiple threads get a better yield out of
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* that one core than a single thread would have,
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* reflect that in sd->smt_gain.
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*/
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if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1)
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if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
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power *= sd->smt_gain;
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power /= weight;
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power >>= SCHED_LOAD_SHIFT;
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}
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sg_inc_cpu_power(sd->groups, power);
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return;
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}
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