/* * itmt.c: Support Intel Turbo Boost Max Technology 3.0 * * (C) Copyright 2016 Intel Corporation * Author: Tim Chen * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; version 2 * of the License. * * 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 #include #include #include #include #include #include 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; /** * 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. */ void sched_set_itmt_support(void) { mutex_lock(&itmt_update_mutex); sched_itmt_capable = true; mutex_unlock(&itmt_update_mutex); } /** * 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. * */ void sched_clear_itmt_support(void) { mutex_lock(&itmt_update_mutex); sched_itmt_capable = false; 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; per_cpu(sched_core_priority, cpu) = smt_prio; i++; } }