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sched/topology: Don't enable EAS on SMT systems 

EAS already requires asymmetric CPU capacities to be enabled, and mixing
this with SMT is an aberration, but better be safe than sorry.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Quentin Perret <qperret@google.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200227191433.31994-2-valentin.schneider@arm.com
This commit is contained in:
Valentin Schneider 2020-02-27 19:14:32 +00:00 committed by Ingo Molnar
parent 0621df3154
commit 38502ab4bf
1 changed files with 10 additions and 2 deletions
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12
kernel/sched/topology.c
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@ -317,8 +317,9 @@ static void sched_energy_set(bool has_eas)
* EAS can be used on a root domain if it meets all the following conditions:
* 1. an Energy Model (EM) is available;
* 2. the SD_ASYM_CPUCAPACITY flag is set in the sched_domain hierarchy.
* 3. the EM complexity is low enough to keep scheduling overheads low;
* 4. schedutil is driving the frequency of all CPUs of the rd;
* 3. no SMT is detected.
* 4. the EM complexity is low enough to keep scheduling overheads low;
* 5. schedutil is driving the frequency of all CPUs of the rd;
*
* The complexity of the Energy Model is defined as:
*
@ -360,6 +361,13 @@ static bool build_perf_domains(const struct cpumask *cpu_map)
goto free;
}
/* EAS definitely does *not* handle SMT */
if (sched_smt_active()) {
pr_warn("rd %*pbl: Disabling EAS, SMT is not supported\n",
cpumask_pr_args(cpu_map));
goto free;
}
for_each_cpu(i, cpu_map) {
/* Skip already covered CPUs. */
if (find_pd(pd, i))