drivers base/arch_topology: provide frequency-invariant accounting support

Implements the arch-specific (arm and arm64) frequency-invariance setter
function arch_set_freq_scale() which provides the following frequency
scaling factor:

  current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_supported_freq(cpu)

One possible consumer of the frequency-invariance getter function
topology_get_freq_scale() is the Per-Entity Load Tracking (PELT)
mechanism of the task scheduler.

Allow inlining of topology_get_freq_scale() into the task scheduler
fast path (e.g. __update_load_avg_se()) by coding it as a static inline
function in the arch topology header file.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index df2bab7de5dbff61542f74f6853249aa360ac41d..06c8009cd0002e60492b3a6bc3670a296e63a47a 100644 (file)
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -22,6 +22,20 @@
 #include <linux/string.h>
 #include <linux/sched/topology.h>
 
+DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
+
+void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
+                        unsigned long max_freq)
+{
+       unsigned long scale;
+       int i;
+
+       scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq;
+
+       for_each_cpu(i, cpus)
+               per_cpu(freq_scale, i) = scale;
+}
+
 static DEFINE_MUTEX(cpu_scale_mutex);
 static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
 

diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index d4fcb0efb896c3e4a40cb527c4da531bc58b3831..e842b33b75f525f6d6ba222a18a50e222f85efe9 100644 (file)
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -5,6 +5,7 @@
 #ifndef _LINUX_ARCH_TOPOLOGY_H_
 #define _LINUX_ARCH_TOPOLOGY_H_
 
+#include <linux/percpu.h>
 #include <linux/types.h>
 
 void topology_normalize_cpu_scale(void);
@@ -17,4 +18,12 @@ unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu);
 
 void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity);
 
+DECLARE_PER_CPU(unsigned long, freq_scale);
+
+static inline
+unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu)
+{
+       return per_cpu(freq_scale, cpu);
+}
+
 #endif /* _LINUX_ARCH_TOPOLOGY_H_ */