diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-26 23:56:10 +0100 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-26 23:56:10 +0100 |
commit | 17bf423a1f2d134187191f0ceb4b395173cc98a7 (patch) | |
tree | df27481f3149103f01ef027aed1bc76e699d6470 /kernel/power | |
parent | Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kern... (diff) | |
parent | sched/fair: Select an energy-efficient CPU on task wake-up (diff) | |
download | linux-17bf423a1f2d134187191f0ceb4b395173cc98a7.tar.xz linux-17bf423a1f2d134187191f0ceb4b395173cc98a7.zip |
Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"The main changes in this cycle were:
- Introduce "Energy Aware Scheduling" - by Quentin Perret.
This is a coherent topology description of CPUs in cooperation with
the PM subsystem, with the goal to schedule more energy-efficiently
on asymetric SMP platform - such as waking up tasks to the more
energy-efficient CPUs first, as long as the system isn't
oversubscribed.
For details of the design, see:
https://lore.kernel.org/lkml/20180724122521.22109-1-quentin.perret@arm.com/
- Misc cleanups and smaller enhancements"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
sched/fair: Select an energy-efficient CPU on task wake-up
sched/fair: Introduce an energy estimation helper function
sched/fair: Add over-utilization/tipping point indicator
sched/fair: Clean-up update_sg_lb_stats parameters
sched/toplogy: Introduce the 'sched_energy_present' static key
sched/topology: Make Energy Aware Scheduling depend on schedutil
sched/topology: Disable EAS on inappropriate platforms
sched/topology: Add lowest CPU asymmetry sched_domain level pointer
sched/topology: Reference the Energy Model of CPUs when available
PM: Introduce an Energy Model management framework
sched/cpufreq: Prepare schedutil for Energy Aware Scheduling
sched/topology: Relocate arch_scale_cpu_capacity() to the internal header
sched/core: Remove unnecessary unlikely() in push_*_task()
sched/topology: Remove the ::smt_gain field from 'struct sched_domain'
sched: Fix various typos in comments
sched/core: Clean up the #ifdef block in add_nr_running()
sched/fair: Make some variables static
sched/core: Create task_has_idle_policy() helper
sched/fair: Add lsub_positive() and use it consistently
sched/fair: Mask UTIL_AVG_UNCHANGED usages
...
Diffstat (limited to 'kernel/power')
-rw-r--r-- | kernel/power/Kconfig | 15 | ||||
-rw-r--r-- | kernel/power/Makefile | 2 | ||||
-rw-r--r-- | kernel/power/energy_model.c | 201 |
3 files changed, 218 insertions, 0 deletions
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index 3a6c2f87699e..f8fe57d1022e 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -298,3 +298,18 @@ config PM_GENERIC_DOMAINS_OF config CPU_PM bool + +config ENERGY_MODEL + bool "Energy Model for CPUs" + depends on SMP + depends on CPU_FREQ + default n + help + Several subsystems (thermal and/or the task scheduler for example) + can leverage information about the energy consumed by CPUs to make + smarter decisions. This config option enables the framework from + which subsystems can access the energy models. + + The exact usage of the energy model is subsystem-dependent. + + If in doubt, say N. diff --git a/kernel/power/Makefile b/kernel/power/Makefile index a3f79f0eef36..e7e47d9be1e5 100644 --- a/kernel/power/Makefile +++ b/kernel/power/Makefile @@ -15,3 +15,5 @@ obj-$(CONFIG_PM_AUTOSLEEP) += autosleep.o obj-$(CONFIG_PM_WAKELOCKS) += wakelock.o obj-$(CONFIG_MAGIC_SYSRQ) += poweroff.o + +obj-$(CONFIG_ENERGY_MODEL) += energy_model.o diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c new file mode 100644 index 000000000000..d9dc2c38764a --- /dev/null +++ b/kernel/power/energy_model.c @@ -0,0 +1,201 @@ +// 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/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); + +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); + + 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); |