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Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kernel/itmt.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/arch/x86/kernel/itmt.c b/arch/x86/kernel/itmt.c new file mode 100644 index 000000000..9ff480e94 --- /dev/null +++ b/arch/x86/kernel/itmt.c @@ -0,0 +1,205 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * itmt.c: Support Intel Turbo Boost Max Technology 3.0 + * + * (C) Copyright 2016 Intel Corporation + * Author: Tim Chen <tim.c.chen@linux.intel.com> + * + * On platforms supporting Intel Turbo Boost Max Technology 3.0, (ITMT), + * the maximum turbo frequencies of some cores in a CPU package may be + * higher than for the other cores in the same package. In that case, + * better performance can be achieved by making the scheduler prefer + * to run tasks on the CPUs with higher max turbo frequencies. + * + * This file provides functions and data structures for enabling the + * scheduler to favor scheduling on cores can be boosted to a higher + * frequency under ITMT. + */ + +#include <linux/sched.h> +#include <linux/cpumask.h> +#include <linux/cpuset.h> +#include <linux/mutex.h> +#include <linux/sysctl.h> +#include <linux/nodemask.h> + +static DEFINE_MUTEX(itmt_update_mutex); +DEFINE_PER_CPU_READ_MOSTLY(int, sched_core_priority); + +/* Boolean to track if system has ITMT capabilities */ +static bool __read_mostly sched_itmt_capable; + +/* + * Boolean to control whether we want to move processes to cpu capable + * of higher turbo frequency for cpus supporting Intel Turbo Boost Max + * Technology 3.0. + * + * It can be set via /proc/sys/kernel/sched_itmt_enabled + */ +unsigned int __read_mostly sysctl_sched_itmt_enabled; + +static int sched_itmt_update_handler(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + unsigned int old_sysctl; + int ret; + + mutex_lock(&itmt_update_mutex); + + if (!sched_itmt_capable) { + mutex_unlock(&itmt_update_mutex); + return -EINVAL; + } + + old_sysctl = sysctl_sched_itmt_enabled; + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + + if (!ret && write && old_sysctl != sysctl_sched_itmt_enabled) { + x86_topology_update = true; + rebuild_sched_domains(); + } + + mutex_unlock(&itmt_update_mutex); + + return ret; +} + +static struct ctl_table itmt_kern_table[] = { + { + .procname = "sched_itmt_enabled", + .data = &sysctl_sched_itmt_enabled, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sched_itmt_update_handler, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + {} +}; + +static struct ctl_table itmt_root_table[] = { + { + .procname = "kernel", + .mode = 0555, + .child = itmt_kern_table, + }, + {} +}; + +static struct ctl_table_header *itmt_sysctl_header; + +/** + * sched_set_itmt_support() - Indicate platform supports ITMT + * + * This function is used by the OS to indicate to scheduler that the platform + * is capable of supporting the ITMT feature. + * + * The current scheme has the pstate driver detects if the system + * is ITMT capable and call sched_set_itmt_support. + * + * This must be done only after sched_set_itmt_core_prio + * has been called to set the cpus' priorities. + * It must not be called with cpu hot plug lock + * held as we need to acquire the lock to rebuild sched domains + * later. + * + * Return: 0 on success + */ +int sched_set_itmt_support(void) +{ + mutex_lock(&itmt_update_mutex); + + if (sched_itmt_capable) { + mutex_unlock(&itmt_update_mutex); + return 0; + } + + itmt_sysctl_header = register_sysctl_table(itmt_root_table); + if (!itmt_sysctl_header) { + mutex_unlock(&itmt_update_mutex); + return -ENOMEM; + } + + sched_itmt_capable = true; + + sysctl_sched_itmt_enabled = 1; + + x86_topology_update = true; + rebuild_sched_domains(); + + mutex_unlock(&itmt_update_mutex); + + return 0; +} + +/** + * sched_clear_itmt_support() - Revoke platform's support of ITMT + * + * This function is used by the OS to indicate that it has + * revoked the platform's support of ITMT feature. + * + * It must not be called with cpu hot plug lock + * held as we need to acquire the lock to rebuild sched domains + * later. + */ +void sched_clear_itmt_support(void) +{ + mutex_lock(&itmt_update_mutex); + + if (!sched_itmt_capable) { + mutex_unlock(&itmt_update_mutex); + return; + } + sched_itmt_capable = false; + + if (itmt_sysctl_header) { + unregister_sysctl_table(itmt_sysctl_header); + itmt_sysctl_header = NULL; + } + + if (sysctl_sched_itmt_enabled) { + /* disable sched_itmt if we are no longer ITMT capable */ + sysctl_sched_itmt_enabled = 0; + x86_topology_update = true; + rebuild_sched_domains(); + } + + mutex_unlock(&itmt_update_mutex); +} + +int arch_asym_cpu_priority(int cpu) +{ + return per_cpu(sched_core_priority, cpu); +} + +/** + * sched_set_itmt_core_prio() - Set CPU priority based on ITMT + * @prio: Priority of cpu core + * @core_cpu: The cpu number associated with the core + * + * The pstate driver will find out the max boost frequency + * and call this function to set a priority proportional + * to the max boost frequency. CPU with higher boost + * frequency will receive higher priority. + * + * No need to rebuild sched domain after updating + * the CPU priorities. The sched domains have no + * dependency on CPU priorities. + */ +void sched_set_itmt_core_prio(int prio, int core_cpu) +{ + int cpu, i = 1; + + for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) { + int smt_prio; + + /* + * Ensure that the siblings are moved to the end + * of the priority chain and only used when + * all other high priority cpus are out of capacity. + */ + smt_prio = prio * smp_num_siblings / (i * i); + per_cpu(sched_core_priority, cpu) = smt_prio; + i++; + } +} |