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authorValentin Schneider <valentin.schneider@arm.com>2020-09-01 21:55:49 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2020-09-18 19:11:20 +0200
commit15e5d5b45b2b7072214af519357a1c0af078c50b (patch)
treefb789f8414a2416450482dc4b751aeda4da11182 /include/linux/arch_topology.h
parentecddc3a0d5d752071c627aa1a1d4d7b529ddae67 (diff)
arch_topology, arm, arm64: define arch_scale_freq_invariant()
arch_scale_freq_invariant() is used by schedutil to determine whether the scheduler's load-tracking signals are frequency invariant. Its definition is overridable, though by default it is hardcoded to 'true' if arch_scale_freq_capacity() is defined ('false' otherwise). This behaviour is not overridden on arm, arm64 and other users of the generic arch topology driver, which is somewhat precarious: arch_scale_freq_capacity() will always be defined, yet not all cpufreq drivers are guaranteed to drive the frequency invariance scale factor setting. In other words, the load-tracking signals may very well *not* be frequency invariant. Now that cpufreq can be queried on whether the current driver is driving the Frequency Invariance (FI) scale setting, the current situation can be improved. This combines the query of whether cpufreq supports the setting of the frequency scale factor, with whether all online CPUs are counter-based FI enabled. While cpufreq FI enablement applies at system level, for all CPUs, counter-based FI support could also be used for only a subset of CPUs to set the invariance scale factor. Therefore, if cpufreq-based FI support is present, we consider the system to be invariant. If missing, we require all online CPUs to be counter-based FI enabled in order for the full system to be considered invariant. If the system ends up not being invariant, a new condition is needed in the counter initialization code that disables all scale factor setting based on counters. Precedence of counters over cpufreq use is not important here. The invariant status is only given to the system if all CPUs have at least one method of setting the frequency scale factor. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'include/linux/arch_topology.h')
-rw-r--r--include/linux/arch_topology.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 810c83336257..083df331a3c9 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -30,6 +30,8 @@ static inline unsigned long topology_get_freq_scale(int cpu)
return per_cpu(freq_scale, cpu);
}
+bool topology_scale_freq_invariant(void);
+
bool arch_freq_counters_available(const struct cpumask *cpus);
DECLARE_PER_CPU(unsigned long, thermal_pressure);