linux/kernel/power/energy_model.c
Quentin Perret 9cac42d064 PM / EM: Expose the Energy Model in debugfs
The recently introduced Energy Model (EM) framework manages power cost
tables of CPUs. These tables are currently only visible from kernel
space. However, in order to debug the behaviour of subsystems that use
the EM (EAS for example), it is often required to know what the power
costs are from userspace.

For this reason, introduce under /sys/kernel/debug/energy_model a set of
directories representing the performance domains of the system. Each
performance domain contains a set of sub-directories representing the
different capacity states (cs) and their attributes, as well as a file
exposing the related CPUs.

The resulting hierarchy is as follows on Arm juno r0 for example:

    /sys/kernel/debug/energy_model
    ├── pd0
    │   ├── cpus
    │   ├── cs:450000
    │   │   ├── cost
    │   │   ├── frequency
    │   │   └── power
    │   ├── cs:575000
    │   │   ├── cost
    │   │   ├── frequency
    │   │   └── power
    │   ├── cs:700000
    │   │   ├── cost
    │   │   ├── frequency
    │   │   └── power
    │   ├── cs:775000
    │   │   ├── cost
    │   │   ├── frequency
    │   │   └── power
    │   └── cs:850000
    │       ├── cost
    │       ├── frequency
    │       └── power
    └── pd1
        ├── cpus
        ├── cs:1100000
        │   ├── cost
        │   ├── frequency
        │   └── power
        ├── cs:450000
        │   ├── cost
        │   ├── frequency
        │   └── power
        ├── cs:625000
        │   ├── cost
        │   ├── frequency
        │   └── power
        ├── cs:800000
        │   ├── cost
        │   ├── frequency
        │   └── power
        └── cs:950000
            ├── cost
            ├── frequency
            └── power

Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2019-01-23 23:07:57 +01:00

259 lines
6.6 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Energy Model of CPUs
*
* Copyright (c) 2018, Arm ltd.
* Written by: Quentin Perret, Arm ltd.
*/
#define pr_fmt(fmt) "energy_model: " fmt
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/debugfs.h>
#include <linux/energy_model.h>
#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);
#ifdef CONFIG_DEBUG_FS
static struct dentry *rootdir;
static void em_debug_create_cs(struct em_cap_state *cs, struct dentry *pd)
{
struct dentry *d;
char name[24];
snprintf(name, sizeof(name), "cs:%lu", cs->frequency);
/* Create per-cs directory */
d = debugfs_create_dir(name, pd);
debugfs_create_ulong("frequency", 0444, d, &cs->frequency);
debugfs_create_ulong("power", 0444, d, &cs->power);
debugfs_create_ulong("cost", 0444, d, &cs->cost);
}
static int em_debug_cpus_show(struct seq_file *s, void *unused)
{
seq_printf(s, "%*pbl\n", cpumask_pr_args(to_cpumask(s->private)));
return 0;
}
DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);
static void em_debug_create_pd(struct em_perf_domain *pd, int cpu)
{
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);
debugfs_create_file("cpus", 0444, d, pd->cpus, &em_debug_cpus_fops);
/* Create a sub-directory for each capacity state */
for (i = 0; i < pd->nr_cap_states; i++)
em_debug_create_cs(&pd->table[i], d);
}
static int __init em_debug_init(void)
{
/* Create /sys/kernel/debug/energy_model directory */
rootdir = debugfs_create_dir("energy_model", NULL);
return 0;
}
core_initcall(em_debug_init);
#else /* CONFIG_DEBUG_FS */
static void em_debug_create_pd(struct em_perf_domain *pd, int cpu) {}
#endif
static struct em_perf_domain *em_create_pd(cpumask_t *span, 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_cap_state *table;
struct em_perf_domain *pd;
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;
/* Build the list of capacity 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 capacity state of 'cpu' above 'freq' and updates
* 'power' and 'freq' accordingly.
*/
ret = cb->active_power(&power, &freq, cpu);
if (ret) {
pr_err("pd%d: invalid cap. state: %d\n", cpu, ret);
goto free_cs_table;
}
/*
* We expect the driver callback to increase the frequency for
* higher capacity states.
*/
if (freq <= prev_freq) {
pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
goto free_cs_table;
}
/*
* The power returned by active_state() is expected to be
* positive, in milli-watts and to fit into 16 bits.
*/
if (!power || power > EM_CPU_MAX_POWER) {
pr_err("pd%d: invalid power: %lu\n", cpu, power);
goto free_cs_table;
}
table[i].power = power;
table[i].frequency = prev_freq = freq;
/*
* The hertz/watts efficiency ratio should decrease as the
* frequency grows on sane platforms. But this isn't always
* true in practice so warn the user if a higher OPP is more
* power efficient than a lower one.
*/
opp_eff = freq / power;
if (opp_eff >= prev_opp_eff)
pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
cpu, i, i - 1);
prev_opp_eff = opp_eff;
}
/* Compute the cost of each capacity_state. */
fmax = (u64) table[nr_states - 1].frequency;
for (i = 0; i < nr_states; i++) {
table[i].cost = div64_u64(fmax * table[i].power,
table[i].frequency);
}
pd->table = table;
pd->nr_cap_states = nr_states;
cpumask_copy(to_cpumask(pd->cpus), span);
em_debug_create_pd(pd, cpu);
return pd;
free_cs_table:
kfree(table);
free_pd:
kfree(pd);
return NULL;
}
/**
* 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
* exist.
*/
struct em_perf_domain *em_cpu_get(int cpu)
{
return READ_ONCE(per_cpu(em_data, cpu));
}
EXPORT_SYMBOL_GPL(em_cpu_get);
/**
* em_register_perf_domain() - Register the Energy Model of a performance domain
* @span : Mask of CPUs in the performance domain
* @nr_states : Number of capacity states to register
* @cb : Callback functions providing the data of the Energy Model
*
* Create Energy Model tables for a performance domain using the callbacks
* defined in cb.
*
* If multiple clients register the same performance domain, all but the first
* registration will be ignored.
*
* Return 0 on success
*/
int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
struct em_data_callback *cb)
{
unsigned long cap, prev_cap = 0;
struct em_perf_domain *pd;
int cpu, ret = 0;
if (!span || !nr_states || !cb)
return -EINVAL;
/*
* Use a mutex to serialize the registration of performance domains and
* let the driver-defined callback functions sleep.
*/
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;
}
/*
* All CPUs of a domain must have the same micro-architecture
* since they all share the same table.
*/
cap = arch_scale_cpu_capacity(NULL, cpu);
if (prev_cap && prev_cap != cap) {
pr_err("CPUs of %*pbl must have the same capacity\n",
cpumask_pr_args(span));
ret = -EINVAL;
goto unlock;
}
prev_cap = cap;
}
/* Create the performance domain and add it to the Energy Model. */
pd = em_create_pd(span, nr_states, cb);
if (!pd) {
ret = -EINVAL;
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);
}
pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
unlock:
mutex_unlock(&em_pd_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(em_register_perf_domain);