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authorIonela Voinescu <ionela.voinescu@arm.com>2020-03-05 09:06:26 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2020-03-06 16:02:50 +0000
commitcd0ed03a8903a0b0c6fc36e32d133d1ddfe70cd6 (patch)
treef38a10887eed417beb301da5faf125618fddab8a /drivers/base
parentbbce8eaa603236bf958b0d24e6377b3f3b623991 (diff)
arm64: use activity monitors for frequency invariance
The Frequency Invariance Engine (FIE) is providing a frequency scaling correction factor that helps achieve more accurate load-tracking. So far, for arm and arm64 platforms, this scale factor has been obtained based on the ratio between the current frequency and the maximum supported frequency recorded by the cpufreq policy. The setting of this scale factor is triggered from cpufreq drivers by calling arch_set_freq_scale. The current frequency used in computation is the frequency requested by a governor, but it may not be the frequency that was implemented by the platform. This correction factor can also be obtained using a core counter and a constant counter to get information on the performance (frequency based only) obtained in a period of time. This will more accurately reflect the actual current frequency of the CPU, compared with the alternative implementation that reflects the request of a performance level from the OS. Therefore, implement arch_scale_freq_tick to use activity monitors, if present, for the computation of the frequency scale factor. The use of AMU counters depends on: - CONFIG_ARM64_AMU_EXTN - depents on the AMU extension being present - CONFIG_CPU_FREQ - the current frequency obtained using counter information is divided by the maximum frequency obtained from the cpufreq policy. While it is possible to have a combination of CPUs in the system with and without support for activity monitors, the use of counters for frequency invariance is only enabled for a CPU if all related CPUs (CPUs in the same frequency domain) support and have enabled the core and constant activity monitor counters. In this way, there is a clear separation between the policies for which arch_set_freq_scale (cpufreq based FIE) is used, and the policies for which arch_scale_freq_tick (counter based FIE) is used to set the frequency scale factor. For this purpose, a late_initcall_sync is registered to trigger validation work for policies that will enable or disable the use of AMU counters for frequency invariance. If CONFIG_CPU_FREQ is not defined, the use of counters is enabled on all CPUs only if all possible CPUs correctly support the necessary counters. Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com> Reviewed-by: Lukasz Luba <lukasz.luba@arm.com> Acked-by: Sudeep Holla <sudeep.holla@arm.com> Cc: Sudeep Holla <sudeep.holla@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'drivers/base')
-rw-r--r--drivers/base/arch_topology.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 6119e11a9f95..8d63673c1689 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -21,6 +21,10 @@
#include <linux/sched.h>
#include <linux/smp.h>
+__weak bool arch_freq_counters_available(struct cpumask *cpus)
+{
+ return false;
+}
DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
@@ -29,6 +33,14 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
unsigned long scale;
int i;
+ /*
+ * If the use of counters for FIE is enabled, just return as we don't
+ * want to update the scale factor with information from CPUFREQ.
+ * Instead the scale factor will be updated from arch_scale_freq_tick.
+ */
+ if (arch_freq_counters_available(cpus))
+ return;
+
scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq;
for_each_cpu(i, cpus)