![Tim Chen](/assets/img/avatar_default.png)
Scheduling to the max performance core is enabled by default for Turbo Boost Maxt Technology 3.0 capable platforms. Remove the useless sysctl_sched_itmt_enabled check to update sched topology for adding the prioritized core scheduling flag. Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: bp@suse.de Cc: jolsa@redhat.com Cc: linux-acpi@vger.kernel.org Cc: linux-pm@vger.kernel.org Cc: rjw@rjwysocki.net Link: http://lkml.kernel.org/r/1484778629-4404-1-git-send-email-tim.c.chen@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
214 lines
5.4 KiB
C
214 lines
5.4 KiB
C
/*
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* itmt.c: Support Intel Turbo Boost Max Technology 3.0
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*
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* (C) Copyright 2016 Intel Corporation
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* Author: Tim Chen <tim.c.chen@linux.intel.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*
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* On platforms supporting Intel Turbo Boost Max Technology 3.0, (ITMT),
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* the maximum turbo frequencies of some cores in a CPU package may be
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* higher than for the other cores in the same package. In that case,
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* better performance can be achieved by making the scheduler prefer
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* to run tasks on the CPUs with higher max turbo frequencies.
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*
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* This file provides functions and data structures for enabling the
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* scheduler to favor scheduling on cores can be boosted to a higher
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* frequency under ITMT.
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*/
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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#include <linux/cpuset.h>
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#include <linux/mutex.h>
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#include <linux/sched.h>
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#include <linux/sysctl.h>
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#include <linux/nodemask.h>
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static DEFINE_MUTEX(itmt_update_mutex);
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DEFINE_PER_CPU_READ_MOSTLY(int, sched_core_priority);
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/* Boolean to track if system has ITMT capabilities */
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static bool __read_mostly sched_itmt_capable;
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/*
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* Boolean to control whether we want to move processes to cpu capable
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* of higher turbo frequency for cpus supporting Intel Turbo Boost Max
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* Technology 3.0.
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*
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* It can be set via /proc/sys/kernel/sched_itmt_enabled
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*/
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unsigned int __read_mostly sysctl_sched_itmt_enabled;
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static int sched_itmt_update_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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unsigned int old_sysctl;
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int ret;
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mutex_lock(&itmt_update_mutex);
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if (!sched_itmt_capable) {
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mutex_unlock(&itmt_update_mutex);
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return -EINVAL;
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}
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old_sysctl = sysctl_sched_itmt_enabled;
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ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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if (!ret && write && old_sysctl != sysctl_sched_itmt_enabled) {
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x86_topology_update = true;
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rebuild_sched_domains();
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}
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mutex_unlock(&itmt_update_mutex);
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return ret;
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}
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static unsigned int zero;
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static unsigned int one = 1;
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static struct ctl_table itmt_kern_table[] = {
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{
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.procname = "sched_itmt_enabled",
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.data = &sysctl_sched_itmt_enabled,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = sched_itmt_update_handler,
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.extra1 = &zero,
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.extra2 = &one,
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},
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{}
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};
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static struct ctl_table itmt_root_table[] = {
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{
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.procname = "kernel",
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.mode = 0555,
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.child = itmt_kern_table,
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},
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{}
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};
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static struct ctl_table_header *itmt_sysctl_header;
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/**
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* sched_set_itmt_support() - Indicate platform supports ITMT
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*
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* This function is used by the OS to indicate to scheduler that the platform
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* is capable of supporting the ITMT feature.
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*
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* The current scheme has the pstate driver detects if the system
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* is ITMT capable and call sched_set_itmt_support.
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*
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* This must be done only after sched_set_itmt_core_prio
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* has been called to set the cpus' priorities.
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* It must not be called with cpu hot plug lock
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* held as we need to acquire the lock to rebuild sched domains
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* later.
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*
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* Return: 0 on success
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*/
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int sched_set_itmt_support(void)
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{
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mutex_lock(&itmt_update_mutex);
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if (sched_itmt_capable) {
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mutex_unlock(&itmt_update_mutex);
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return 0;
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}
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itmt_sysctl_header = register_sysctl_table(itmt_root_table);
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if (!itmt_sysctl_header) {
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mutex_unlock(&itmt_update_mutex);
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return -ENOMEM;
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}
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sched_itmt_capable = true;
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sysctl_sched_itmt_enabled = 1;
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x86_topology_update = true;
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rebuild_sched_domains();
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mutex_unlock(&itmt_update_mutex);
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return 0;
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}
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/**
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* sched_clear_itmt_support() - Revoke platform's support of ITMT
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*
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* This function is used by the OS to indicate that it has
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* revoked the platform's support of ITMT feature.
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*
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* It must not be called with cpu hot plug lock
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* held as we need to acquire the lock to rebuild sched domains
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* later.
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*/
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void sched_clear_itmt_support(void)
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{
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mutex_lock(&itmt_update_mutex);
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if (!sched_itmt_capable) {
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mutex_unlock(&itmt_update_mutex);
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return;
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}
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sched_itmt_capable = false;
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if (itmt_sysctl_header) {
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unregister_sysctl_table(itmt_sysctl_header);
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itmt_sysctl_header = NULL;
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}
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if (sysctl_sched_itmt_enabled) {
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/* disable sched_itmt if we are no longer ITMT capable */
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sysctl_sched_itmt_enabled = 0;
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x86_topology_update = true;
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rebuild_sched_domains();
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}
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mutex_unlock(&itmt_update_mutex);
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}
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int arch_asym_cpu_priority(int cpu)
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{
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return per_cpu(sched_core_priority, cpu);
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}
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/**
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* sched_set_itmt_core_prio() - Set CPU priority based on ITMT
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* @prio: Priority of cpu core
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* @core_cpu: The cpu number associated with the core
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*
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* The pstate driver will find out the max boost frequency
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* and call this function to set a priority proportional
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* to the max boost frequency. CPU with higher boost
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* frequency will receive higher priority.
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*
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* No need to rebuild sched domain after updating
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* the CPU priorities. The sched domains have no
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* dependency on CPU priorities.
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*/
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void sched_set_itmt_core_prio(int prio, int core_cpu)
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{
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int cpu, i = 1;
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for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) {
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int smt_prio;
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/*
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* Ensure that the siblings are moved to the end
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* of the priority chain and only used when
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* all other high priority cpus are out of capacity.
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*/
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smt_prio = prio * smp_num_siblings / i;
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per_cpu(sched_core_priority, cpu) = smt_prio;
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i++;
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}
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}
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