[PATCH v7 04/15] PM / EM: add support for other devices than CPUs in Energy Model

From: Lukasz Luba
Date: Mon May 11 2020 - 07:20:21 EST

Add support for other devices that CPUs. The registration function
does not require a valid cpumask pointer and is ready to handle new
devices. Some of the internal structures has been reorganized in order to
keep consistent view (like removing per_cpu pd pointers). To track usage
of the Energy Model structures, they are protected with kref.

Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>
---
include/linux/device.h | 5 +
include/linux/energy_model.h | 28 +++--
kernel/power/energy_model.c | 237 ++++++++++++++++++++++++-----------
3 files changed, 187 insertions(+), 83 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index ac8e37cd716a..7023d3ea189b 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -13,6 +13,7 @@
#define _DEVICE_H_

#include <linux/dev_printk.h>
+#include <linux/energy_model.h>
#include <linux/ioport.h>
#include <linux/kobject.h>
#include <linux/klist.h>
@@ -559,6 +560,10 @@ struct device {
struct dev_pm_info power;
struct dev_pm_domain *pm_domain;

+#ifdef CONFIG_ENERGY_MODEL
+ struct em_perf_domain *em_pd;
+#endif
+
#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
struct irq_domain *msi_domain;
#endif
diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index 7076cb22b247..f5a88486d1c4 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -12,8 +12,10 @@

/**
* em_perf_state - Performance state of a performance domain
- * @frequency: The CPU frequency in KHz, for consistency with CPUFreq
- * @power: The power consumed by 1 CPU at this level, in milli-watts
+ * @frequency: The frequency in KHz, for consistency with CPUFreq
+ * @power: The power consumed at this level, in milli-watts (by 1 CPU or
+ by a registered device). It can be a total power: static and
+ dynamic.
* @cost: The cost coefficient associated with this level, used during
* energy calculation. Equal to: power * max_frequency / frequency
*/
@@ -27,12 +29,15 @@ struct em_perf_state {
* em_perf_domain - Performance domain
* @table: List of performance states, in ascending order
* @nr_perf_states: Number of performance states
- * @cpus: Cpumask covering the CPUs of the domain
+ * @cpus: Cpumask covering the CPUs of the domain. It's here
+ * for performance reasons to avoid potential cache
+ * misses during energy calculations in the scheduler
*
- * A "performance domain" represents a group of CPUs whose performance is
- * scaled together. All CPUs of a performance domain must have the same
- * micro-architecture. Performance domains often have a 1-to-1 mapping with
- * CPUFreq policies.
+ * In case of CPU device, a "performance domain" represents a group of CPUs
+ * whose performance is scaled together. All CPUs of a performance domain
+ * must have the same micro-architecture. Performance domains often have
+ * a 1-to-1 mapping with CPUFreq policies. In case of other devices the 'cpus'
+ * field is unused.
*/
struct em_perf_domain {
struct em_perf_state *table;
@@ -71,10 +76,12 @@ struct em_data_callback {
#define EM_DATA_CB(_active_power_cb) { .active_power = &_active_power_cb }

struct em_perf_domain *em_cpu_get(int cpu);
+struct em_perf_domain *em_pd_get(struct device *dev);
int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
struct em_data_callback *cb);
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
struct em_data_callback *cb, cpumask_t *span);
+void em_dev_unregister_perf_domain(struct device *dev);

/**
* em_pd_energy() - Estimates the energy consumed by the CPUs of a perf. domain
@@ -184,10 +191,17 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
{
return -EINVAL;
}
+static inline void em_dev_unregister_perf_domain(struct device *dev)
+{
+}
static inline struct em_perf_domain *em_cpu_get(int cpu)
{
return NULL;
}
+static inline struct em_perf_domain *em_pd_get(struct device *dev)
+{
+ return NULL;
+}
static inline unsigned long em_pd_energy(struct em_perf_domain *pd,
unsigned long max_util, unsigned long sum_util)
{
diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index 5b8a1566526a..9cc7f2973600 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -2,8 +2,9 @@
/*
* Energy Model of CPUs
*
- * Copyright (c) 2018, Arm ltd.
+ * Copyright (c) 2018-2020, Arm ltd.
* Written by: Quentin Perret, Arm ltd.
+ * Improvements provided by: Lukasz Luba, Arm ltd.
*/

#define pr_fmt(fmt) "energy_model: " fmt
@@ -15,15 +16,17 @@
#include <linux/sched/topology.h>
#include <linux/slab.h>

-/* Mapping of each CPU to the performance domain to which it belongs. */
-static DEFINE_PER_CPU(struct em_perf_domain *, em_data);
-
/*
* Mutex serializing the registrations of performance domains and letting
* callbacks defined by drivers sleep.
*/
static DEFINE_MUTEX(em_pd_mutex);

+static bool _is_cpu_device(struct device *dev)
+{
+ return (dev->bus == &cpu_subsys);
+}
+
#ifdef CONFIG_DEBUG_FS
static struct dentry *rootdir;

@@ -49,22 +52,30 @@ static int em_debug_cpus_show(struct seq_file *s, void *unused)
}
DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);

-static void em_debug_create_pd(struct em_perf_domain *pd, int cpu)
+static void em_debug_create_pd(struct device *dev)
{
struct dentry *d;
- char name[8];
int i;

- snprintf(name, sizeof(name), "pd%d", cpu);
-
/* Create the directory of the performance domain */
- d = debugfs_create_dir(name, rootdir);
+ d = debugfs_create_dir(dev_name(dev), rootdir);

- debugfs_create_file("cpus", 0444, d, pd->cpus, &em_debug_cpus_fops);
+ if (_is_cpu_device(dev))
+ debugfs_create_file("cpus", 0444, d, dev->em_pd->cpus,
+ &em_debug_cpus_fops);

/* Create a sub-directory for each performance state */
- for (i = 0; i < pd->nr_perf_states; i++)
- em_debug_create_ps(&pd->table[i], d);
+ for (i = 0; i < dev->em_pd->nr_perf_states; i++)
+ em_debug_create_ps(&dev->em_pd->table[i], d);
+
+}
+
+static void em_debug_remove_pd(struct device *dev)
+{
+ struct dentry *debug_dir;
+
+ debug_dir = debugfs_lookup(dev_name(dev), rootdir);
+ debugfs_remove_recursive(debug_dir);
}

static int __init em_debug_init(void)
@@ -76,40 +87,34 @@ static int __init em_debug_init(void)
}
core_initcall(em_debug_init);
#else /* CONFIG_DEBUG_FS */
-static void em_debug_create_pd(struct em_perf_domain *pd, int cpu) {}
+static void em_debug_create_pd(struct device *dev) {}
+static void em_debug_remove_pd(struct device *dev) {}
#endif
-static struct em_perf_domain *
-em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
- cpumask_t *span)
+
+static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
+ int nr_states, struct em_data_callback *cb)
{
unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
unsigned long power, freq, prev_freq = 0;
- int i, ret, cpu = cpumask_first(span);
struct em_perf_state *table;
- struct em_perf_domain *pd;
+ int i, ret;
u64 fmax;

- if (!cb->active_power)
- return NULL;
-
- pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
- if (!pd)
- return NULL;
-
table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
if (!table)
- goto free_pd;
+ return -ENOMEM;

/* Build the list of performance states for this performance domain */
for (i = 0, freq = 0; i < nr_states; i++, freq++) {
/*
* active_power() is a driver callback which ceils 'freq' to
- * lowest performance state of 'cpu' above 'freq' and updates
+ * lowest performance state of 'dev' above 'freq' and updates
* 'power' and 'freq' accordingly.
*/
ret = cb->active_power(&power, &freq, dev);
if (ret) {
- pr_err("pd%d: invalid perf. state: %d\n", cpu, ret);
+ dev_err(dev, "EM: invalid perf. state: %d\n",
+ ret);
goto free_ps_table;
}

@@ -118,7 +123,8 @@ em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
* higher performance states.
*/
if (freq <= prev_freq) {
- pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
+ dev_err(dev, "EM: non-increasing freq: %lu\n",
+ freq);
goto free_ps_table;
}

@@ -127,7 +133,8 @@ em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
* positive, in milli-watts and to fit into 16 bits.
*/
if (!power || power > EM_MAX_POWER) {
- pr_err("pd%d: invalid power: %lu\n", cpu, power);
+ dev_err(dev, "EM: invalid power: %lu\n",
+ power);
goto free_ps_table;
}

@@ -142,8 +149,8 @@ em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
*/
opp_eff = freq / power;
if (opp_eff >= prev_opp_eff)
- pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
- cpu, i, i - 1);
+ dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
+ i, i - 1);
prev_opp_eff = opp_eff;
}

@@ -156,30 +163,82 @@ em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,

pd->table = table;
pd->nr_perf_states = nr_states;
- cpumask_copy(to_cpumask(pd->cpus), span);
-
- em_debug_create_pd(pd, cpu);

- return pd;
+ return 0;

free_ps_table:
kfree(table);
-free_pd:
- kfree(pd);
+ return -EINVAL;
+}
+
+static int em_create_pd(struct device *dev, int nr_states,
+ struct em_data_callback *cb, cpumask_t *cpus)
+{
+ struct em_perf_domain *pd;
+ struct device *cpu_dev;
+ int cpu, ret;
+
+ if (_is_cpu_device(dev)) {
+ pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
+ if (!pd)
+ return -ENOMEM;
+
+ cpumask_copy(em_span_cpus(pd), cpus);
+ } else {
+ pd = kzalloc(sizeof(*pd), GFP_KERNEL);
+ if (!pd)
+ return -ENOMEM;
+ }
+
+ ret = em_create_perf_table(dev, pd, nr_states, cb);
+ if (ret) {
+ kfree(pd);
+ return ret;
+ }

- return NULL;
+ if (_is_cpu_device(dev))
+ for_each_cpu(cpu, cpus) {
+ cpu_dev = get_cpu_device(cpu);
+ cpu_dev->em_pd = pd;
+ }
+ else
+ dev->em_pd = pd;
+
+ return 0;
}

+/**
+ * em_pd_get() - Return the performance domain for a device
+ * @dev : Device to find the performance domain for
+ *
+ * Returns the performance domain to which 'dev' belongs, or NULL if it doesn't
+ * exist.
+ */
+struct em_perf_domain *em_pd_get(struct device *dev)
+{
+ if (IS_ERR_OR_NULL(dev))
+ return NULL;
+
+ return dev->em_pd;
+}
+EXPORT_SYMBOL_GPL(em_pd_get);
+
/**
* em_cpu_get() - Return the performance domain for a CPU
* @cpu : CPU to find the performance domain for
*
- * Return: the performance domain to which 'cpu' belongs, or NULL if it doesn't
+ * Returns the performance domain to which 'cpu' belongs, or NULL if it doesn't
* exist.
*/
struct em_perf_domain *em_cpu_get(int cpu)
{
- return READ_ONCE(per_cpu(em_data, cpu));
+ struct device *cpu_dev;
+
+ cpu_dev = get_cpu_device(cpu);
+ if (!cpu_dev)
+ return NULL;
+
+ return em_pd_get(cpu_dev);
}
EXPORT_SYMBOL_GPL(em_cpu_get);

@@ -188,7 +247,7 @@ EXPORT_SYMBOL_GPL(em_cpu_get);
* @dev : Device for which the EM is to register
* @nr_states : Number of performance states to register
* @cb : Callback functions providing the data of the Energy Model
- * @span : Pointer to cpumask_t, which in case of a CPU device is
+ * @cpus : Pointer to cpumask_t, which in case of a CPU device is
* obligatory. It can be taken from i.e. 'policy->cpus'. For other
* type of devices this should be set to NULL.
*
@@ -201,13 +260,12 @@ EXPORT_SYMBOL_GPL(em_cpu_get);
* Return 0 on success
*/
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
- struct em_data_callback *cb, cpumask_t *span)
+ struct em_data_callback *cb, cpumask_t *cpus)
{
unsigned long cap, prev_cap = 0;
- struct em_perf_domain *pd;
- int cpu, ret = 0;
+ int cpu, ret;

- if (!dev || !span || !nr_states || !cb)
+ if (!dev || !nr_states || !cb)
return -EINVAL;

/*
@@ -216,47 +274,50 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
*/
mutex_lock(&em_pd_mutex);

- for_each_cpu(cpu, span) {
- /* Make sure we don't register again an existing domain. */
- if (READ_ONCE(per_cpu(em_data, cpu))) {
- ret = -EEXIST;
- goto unlock;
- }
+ if (dev->em_pd) {
+ ret = -EEXIST;
+ goto unlock;
+ }

- /*
- * All CPUs of a domain must have the same micro-architecture
- * since they all share the same table.
- */
- cap = arch_scale_cpu_capacity(cpu);
- if (prev_cap && prev_cap != cap) {
- pr_err("CPUs of %*pbl must have the same capacity\n",
- cpumask_pr_args(span));
+ if (_is_cpu_device(dev)) {
+ if (!cpus) {
+ dev_err(dev, "EM: invalid CPU mask\n");
ret = -EINVAL;
goto unlock;
}
- prev_cap = cap;
+
+ for_each_cpu(cpu, cpus) {
+ if (em_cpu_get(cpu)) {
+ dev_err(dev, "EM: exists for CPU%d\n", cpu);
+ ret = -EEXIST;
+ goto unlock;
+ }
+ /*
+ * All CPUs of a domain must have the same
+ * micro-architecture since they all share the same
+ * table.
+ */
+ cap = arch_scale_cpu_capacity(cpu);
+ if (prev_cap && prev_cap != cap) {
+ dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n",
+ cpumask_pr_args(cpus));
+
+ ret = -EINVAL;
+ goto unlock;
+ }
+ prev_cap = cap;
+ }
}

- /* Create the performance domain and add it to the Energy Model. */
- pd = em_create_pd(dev, nr_states, cb, span);
- if (!pd) {
- ret = -EINVAL;
+ ret = em_create_pd(dev, nr_states, cb, cpus);
+ if (ret)
goto unlock;
- }

- for_each_cpu(cpu, span) {
- /*
- * The per-cpu array can be read concurrently from em_cpu_get().
- * The barrier enforces the ordering needed to make sure readers
- * can only access well formed em_perf_domain structs.
- */
- smp_store_release(per_cpu_ptr(&em_data, cpu), pd);
- }
+ em_debug_create_pd(dev);
+ dev_info(dev, "EM: created perf domain\n");

- pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
unlock:
mutex_unlock(&em_pd_mutex);
-
return ret;
}
EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
@@ -285,3 +346,27 @@ int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
return em_dev_register_perf_domain(cpu_dev, nr_states, cb, span);
}
EXPORT_SYMBOL_GPL(em_register_perf_domain);
+
+/**
+ * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
+ * @dev : Device for which the EM is registered
+ *
+ * Try to unregister the EM for the specified device (but not a CPU).
+ */
+void em_dev_unregister_perf_domain(struct device *dev)
+{
+ if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
+ return;
+
+ if (_is_cpu_device(dev))
+ return;
+
+ mutex_lock(&em_pd_mutex);
+ em_debug_remove_pd(dev);
+
+ kfree(dev->em_pd->table);
+ kfree(dev->em_pd);
+ dev->em_pd = NULL;
+ mutex_unlock(&em_pd_mutex);
+}
+EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);
--
2.17.1