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Message-Id: <1580250967-4386-4-git-send-email-thara.gopinath@linaro.org>
Date: Tue, 28 Jan 2020 17:36:02 -0500
From: Thara Gopinath <thara.gopinath@...aro.org>
To: mingo@...hat.com, peterz@...radead.org, ionela.voinescu@....com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
rui.zhang@...el.com, qperret@...gle.com, daniel.lezcano@...aro.org,
viresh.kumar@...aro.org, rostedt@...dmis.org, will@...nel.org,
catalin.marinas@....com, sudeep.holla@....com,
juri.lelli@...hat.com, corbet@....net
Cc: linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
javi.merino@...nel.org, amit.kucheria@...durent.com
Subject: [Patch v9 3/8] arm,arm64,drivers:Add infrastructure to store and update instantaneous thermal pressure
Add architecture specific APIs to update and track thermal pressure on a
per cpu basis. A per cpu variable thermal_pressure is introduced to keep
track of instantaneous per cpu thermal pressure. Thermal pressure is the
delta between maximum capacity and capped capacity due to a thermal event.
topology_get_thermal_pressure can be hooked into the scheduler specified
arch_cpu_thermal_capacity to retrieve instantaneous thermal pressure of a
cpu.
arch_set_thermal_pressure can be used to update the thermal pressure.
Considering topology_get_thermal_pressure reads thermal_pressure and
arch_set_thermal_pressure writes into thermal_pressure, one can argue for
some sort of locking mechanism to avoid a stale value. But considering
topology_get_thermal_pressure can be called from a system critical path
like scheduler tick function, a locking mechanism is not ideal. This means
that it is possible the thermal_pressure value used to calculate average
thermal pressure for a cpu can be stale for upto 1 tick period.
Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
---
v6->v7:
- Changed the input argument in arch_set_thermal_pressure from
capped capacity to delta capacity(thermal pressure) as per
Ionela's review comments.
arch/arm/include/asm/topology.h | 3 +++
arch/arm64/include/asm/topology.h | 3 +++
drivers/base/arch_topology.c | 11 +++++++++++
include/linux/arch_topology.h | 10 ++++++++++
4 files changed, 27 insertions(+)
diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
index 8a0fae9..3a50a19 100644
--- a/arch/arm/include/asm/topology.h
+++ b/arch/arm/include/asm/topology.h
@@ -16,6 +16,9 @@
/* Enable topology flag updates */
#define arch_update_cpu_topology topology_update_cpu_topology
+/* Replace task scheduler's default thermal pressure retrieve API */
+#define arch_cpu_thermal_pressure topology_get_thermal_pressure
+
#else
static inline void init_cpu_topology(void) { }
diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
index a4d945d..a70896f 100644
--- a/arch/arm64/include/asm/topology.h
+++ b/arch/arm64/include/asm/topology.h
@@ -25,6 +25,9 @@ int pcibus_to_node(struct pci_bus *bus);
/* Enable topology flag updates */
#define arch_update_cpu_topology topology_update_cpu_topology
+/* Replace task scheduler's default thermal pressure retrieve API */
+#define arch_cpu_thermal_pressure topology_get_thermal_pressure
+
#include <asm-generic/topology.h>
#endif /* _ASM_ARM_TOPOLOGY_H */
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 6119e11..68dfa49 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -42,6 +42,17 @@ void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
per_cpu(cpu_scale, cpu) = capacity;
}
+DEFINE_PER_CPU(unsigned long, thermal_pressure);
+
+void arch_set_thermal_pressure(struct cpumask *cpus,
+ unsigned long th_pressure)
+{
+ int cpu;
+
+ for_each_cpu(cpu, cpus)
+ WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure);
+}
+
static ssize_t cpu_capacity_show(struct device *dev,
struct device_attribute *attr,
char *buf)
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 3015ecb..88a115e 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -33,6 +33,16 @@ unsigned long topology_get_freq_scale(int cpu)
return per_cpu(freq_scale, cpu);
}
+DECLARE_PER_CPU(unsigned long, thermal_pressure);
+
+static inline unsigned long topology_get_thermal_pressure(int cpu)
+{
+ return per_cpu(thermal_pressure, cpu);
+}
+
+void arch_set_thermal_pressure(struct cpumask *cpus,
+ unsigned long th_pressure);
+
struct cpu_topology {
int thread_id;
int core_id;
--
2.1.4
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