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Message-ID: <CAKfTPtDB=5mQnJfzES+iU-nmNjVDM48f_iKuc7WefkRVWW4JOQ@mail.gmail.com>
Date: Mon, 12 Jun 2017 16:27:30 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
Russell King - ARM Linux <linux@....linux.org.uk>,
LAK <linux-arm-kernel@...ts.infradead.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Russell King <rmk+kernel@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Juri Lelli <juri.lelli@....com>,
Vincent Guittot <vincent.guittot@...aor.org>,
Peter Zijlstra <peterz@...radead.org>,
Morten Rasmussen <morten.rasmussen@....com>
Subject: Re: [PATCH 2/6] drivers base/arch_topology: frequency-invariant
load-tracking support
On 8 June 2017 at 09:55, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
> Implements an arch-specific frequency-scaling function
> topology_get_freq_scale() which provides the following frequency
> scaling factor:
>
> current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_supported_freq(cpu)
>
> The debug output in init_cpu_capacity_callback() has been changed to be
> able to distinguish whether cpu capacity and max frequency or only max
> frequency has been set. The latter case happens on systems where there
> is no or broken cpu capacity binding (cpu node property
> capacity-dmips-mhz) information.
>
> One possible consumer of this is the Per-Entity Load Tracking (PELT)
> mechanism of the task scheduler.
>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Juri Lelli <juri.lelli@....com>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
> ---
> drivers/base/arch_topology.c | 52 ++++++++++++++++++++++++++++++++++++++++---
> include/linux/arch_topology.h | 2 ++
> 2 files changed, 51 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 272831c89feb..f6f14670bdab 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -24,12 +24,18 @@
>
> static DEFINE_MUTEX(cpu_scale_mutex);
> static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
> +static DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
>
> unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu)
> {
> return per_cpu(cpu_scale, cpu);
> }
>
> +unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu)
> +{
> + return per_cpu(freq_scale, cpu);
> +}
> +
> void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
> {
> per_cpu(cpu_scale, cpu) = capacity;
> @@ -164,6 +170,7 @@ static cpumask_var_t cpus_to_visit;
> static bool cap_parsing_done;
> static void parsing_done_workfn(struct work_struct *work);
> static DECLARE_WORK(parsing_done_work, parsing_done_workfn);
> +static DEFINE_PER_CPU(unsigned long, max_freq);
>
> static int
> init_cpu_capacity_callback(struct notifier_block *nb,
> @@ -185,6 +192,7 @@ init_cpu_capacity_callback(struct notifier_block *nb,
> cpus_to_visit,
> policy->related_cpus);
> for_each_cpu(cpu, policy->related_cpus) {
> + per_cpu(max_freq, cpu) = policy->cpuinfo.max_freq;
> if (cap_parsing_failed)
> continue;
> raw_capacity[cpu] = topology_get_cpu_scale(NULL, cpu) *
> @@ -195,8 +203,10 @@ init_cpu_capacity_callback(struct notifier_block *nb,
> if (!cap_parsing_failed) {
> topology_normalize_cpu_scale();
> kfree(raw_capacity);
> + pr_debug("cpu_capacity: parsing done\n");
> + } else {
> + pr_debug("cpu_capacity: max frequency parsing done\n");
> }
> - pr_debug("cpu_capacity: parsing done\n");
> cap_parsing_done = true;
> schedule_work(&parsing_done_work);
> }
> @@ -208,8 +218,38 @@ static struct notifier_block init_cpu_capacity_notifier = {
> .notifier_call = init_cpu_capacity_callback,
> };
>
> +static void set_freq_scale(unsigned int cpu, unsigned long freq)
> +{
> + unsigned long max = per_cpu(max_freq, cpu);
> +
> + if (!max)
> + return;
> +
> + per_cpu(freq_scale, cpu) = (freq << SCHED_CAPACITY_SHIFT) / max;
> +}
> +
> +static int set_freq_scale_callback(struct notifier_block *nb,
> + unsigned long val,
> + void *data)
> +{
> + struct cpufreq_freqs *freq = data;
> +
> + switch (val) {
> + case CPUFREQ_PRECHANGE:
> + set_freq_scale(freq->cpu, freq->new);
> + }
> +
> + return 0;
> +}
> +
> +static struct notifier_block set_freq_scale_notifier = {
> + .notifier_call = set_freq_scale_callback,
> +};
> +
> static int __init register_cpufreq_notifier(void)
> {
> + int ret;
> +
> /*
> * on ACPI-based systems we need to use the default cpu capacity
> * until we have the necessary code to parse the cpu capacity, so
> @@ -225,8 +265,14 @@ static int __init register_cpufreq_notifier(void)
>
> cpumask_copy(cpus_to_visit, cpu_possible_mask);
>
> - return cpufreq_register_notifier(&init_cpu_capacity_notifier,
> - CPUFREQ_POLICY_NOTIFIER);
> + ret = cpufreq_register_notifier(&init_cpu_capacity_notifier,
> + CPUFREQ_POLICY_NOTIFIER);
> +
> + if (ret)
Don't you have to free memory allocated for cpus_to_visit in case of
errot ? it was not done before your patch as well
> + return ret;
> +
> + return cpufreq_register_notifier(&set_freq_scale_notifier,
> + CPUFREQ_TRANSITION_NOTIFIER);
Don't you have to unregister the other cpufreq notifier if an error is
returned and free the mem allocated for cpus_to_visit ?
> }
> core_initcall(register_cpufreq_notifier);
>
> diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> index 9af3c174c03a..3fb4d8ccb179 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -12,6 +12,8 @@ int topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu);
> struct sched_domain;
> unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu);
>
> +unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu);
> +
> void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity);
>
> #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
> --
> 2.11.0
>
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