| Message ID | 20200722093732.14297-7-ionela.voinescu@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | cpufreq: improve frequency invariance support | expand |
On Wed, Jul 22, 2020 at 10:37:31AM +0100, Ionela Voinescu wrote: > From: Valentin Schneider <valentin.schneider@arm.com> > > 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> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Sudeep Holla <sudeep.holla@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h index 435aba289fc5..d59458e97c6d 100644 --- a/arch/arm/include/asm/topology.h +++ b/arch/arm/include/asm/topology.h @@ -9,6 +9,7 @@ /* Replace task scheduler's default frequency-invariant accounting */ #define arch_scale_freq_capacity topology_get_freq_scale +#define arch_scale_freq_invariant topology_scale_freq_invariant /* Replace task scheduler's default cpu-invariant accounting */ #define arch_scale_cpu_capacity topology_get_cpu_scale diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h index 0cc835ddfcd1..b67081c0dcfb 100644 --- a/arch/arm64/include/asm/topology.h +++ b/arch/arm64/include/asm/topology.h @@ -27,6 +27,7 @@ void topology_scale_freq_tick(void); /* Replace task scheduler's default frequency-invariant accounting */ #define arch_scale_freq_capacity topology_get_freq_scale +#define arch_scale_freq_invariant topology_scale_freq_invariant /* Replace task scheduler's default cpu-invariant accounting */ #define arch_scale_cpu_capacity topology_get_cpu_scale diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index 9a9f2b8dedf5..4064d39bb66d 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -246,6 +246,13 @@ static int __init init_amu_fie(void) static_branch_enable(&amu_fie_key); } + /* + * If the system is not fully invariant after AMU init, disable + * partial use of counters for frequency invariance. + */ + if (!topology_scale_freq_invariant()) + static_branch_disable(&amu_fie_key); + free_valid_mask: free_cpumask_var(valid_cpus); diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 3ad59e38f3f3..30b67bb820c5 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -21,6 +21,12 @@ #include <linux/sched.h> #include <linux/smp.h> +bool topology_scale_freq_invariant(void) +{ + return cpufreq_sets_freq_scale() || + arch_freq_counters_available(cpu_online_mask); +} + __weak bool arch_freq_counters_available(const struct cpumask *cpus) { return false; diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h index 4be0315700cb..5bc55cfc9399 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);