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b886d83c | 1 | // SPDX-License-Identifier: GPL-2.0-only |
5e76b2ab TC |
2 | /* |
3 | * itmt.c: Support Intel Turbo Boost Max Technology 3.0 | |
4 | * | |
5 | * (C) Copyright 2016 Intel Corporation | |
6 | * Author: Tim Chen <tim.c.chen@linux.intel.com> | |
7 | * | |
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8 | * On platforms supporting Intel Turbo Boost Max Technology 3.0, (ITMT), |
9 | * the maximum turbo frequencies of some cores in a CPU package may be | |
10 | * higher than for the other cores in the same package. In that case, | |
11 | * better performance can be achieved by making the scheduler prefer | |
12 | * to run tasks on the CPUs with higher max turbo frequencies. | |
13 | * | |
14 | * This file provides functions and data structures for enabling the | |
15 | * scheduler to favor scheduling on cores can be boosted to a higher | |
16 | * frequency under ITMT. | |
17 | */ | |
18 | ||
19 | #include <linux/sched.h> | |
20 | #include <linux/cpumask.h> | |
21 | #include <linux/cpuset.h> | |
a293b395 | 22 | #include <linux/mutex.h> |
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23 | #include <linux/sysctl.h> |
24 | #include <linux/nodemask.h> | |
25 | ||
26 | static DEFINE_MUTEX(itmt_update_mutex); | |
27 | DEFINE_PER_CPU_READ_MOSTLY(int, sched_core_priority); | |
28 | ||
29 | /* Boolean to track if system has ITMT capabilities */ | |
30 | static bool __read_mostly sched_itmt_capable; | |
31 | ||
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32 | /* |
33 | * Boolean to control whether we want to move processes to cpu capable | |
34 | * of higher turbo frequency for cpus supporting Intel Turbo Boost Max | |
35 | * Technology 3.0. | |
36 | * | |
37 | * It can be set via /proc/sys/kernel/sched_itmt_enabled | |
38 | */ | |
39 | unsigned int __read_mostly sysctl_sched_itmt_enabled; | |
40 | ||
41 | static int sched_itmt_update_handler(struct ctl_table *table, int write, | |
32927393 | 42 | void *buffer, size_t *lenp, loff_t *ppos) |
f9793e34 TC |
43 | { |
44 | unsigned int old_sysctl; | |
45 | int ret; | |
46 | ||
47 | mutex_lock(&itmt_update_mutex); | |
48 | ||
49 | if (!sched_itmt_capable) { | |
50 | mutex_unlock(&itmt_update_mutex); | |
51 | return -EINVAL; | |
52 | } | |
53 | ||
54 | old_sysctl = sysctl_sched_itmt_enabled; | |
55 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
56 | ||
57 | if (!ret && write && old_sysctl != sysctl_sched_itmt_enabled) { | |
58 | x86_topology_update = true; | |
59 | rebuild_sched_domains(); | |
60 | } | |
61 | ||
62 | mutex_unlock(&itmt_update_mutex); | |
63 | ||
64 | return ret; | |
65 | } | |
66 | ||
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67 | static struct ctl_table itmt_kern_table[] = { |
68 | { | |
69 | .procname = "sched_itmt_enabled", | |
70 | .data = &sysctl_sched_itmt_enabled, | |
71 | .maxlen = sizeof(unsigned int), | |
72 | .mode = 0644, | |
73 | .proc_handler = sched_itmt_update_handler, | |
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74 | .extra1 = SYSCTL_ZERO, |
75 | .extra2 = SYSCTL_ONE, | |
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76 | }, |
77 | {} | |
78 | }; | |
79 | ||
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80 | static struct ctl_table_header *itmt_sysctl_header; |
81 | ||
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82 | /** |
83 | * sched_set_itmt_support() - Indicate platform supports ITMT | |
84 | * | |
85 | * This function is used by the OS to indicate to scheduler that the platform | |
86 | * is capable of supporting the ITMT feature. | |
87 | * | |
88 | * The current scheme has the pstate driver detects if the system | |
89 | * is ITMT capable and call sched_set_itmt_support. | |
90 | * | |
91 | * This must be done only after sched_set_itmt_core_prio | |
92 | * has been called to set the cpus' priorities. | |
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93 | * It must not be called with cpu hot plug lock |
94 | * held as we need to acquire the lock to rebuild sched domains | |
95 | * later. | |
96 | * | |
97 | * Return: 0 on success | |
5e76b2ab | 98 | */ |
f9793e34 | 99 | int sched_set_itmt_support(void) |
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100 | { |
101 | mutex_lock(&itmt_update_mutex); | |
102 | ||
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103 | if (sched_itmt_capable) { |
104 | mutex_unlock(&itmt_update_mutex); | |
105 | return 0; | |
106 | } | |
107 | ||
89d7971e | 108 | itmt_sysctl_header = register_sysctl("kernel", itmt_kern_table); |
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109 | if (!itmt_sysctl_header) { |
110 | mutex_unlock(&itmt_update_mutex); | |
111 | return -ENOMEM; | |
112 | } | |
113 | ||
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114 | sched_itmt_capable = true; |
115 | ||
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116 | sysctl_sched_itmt_enabled = 1; |
117 | ||
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118 | x86_topology_update = true; |
119 | rebuild_sched_domains(); | |
f9793e34 | 120 | |
5e76b2ab | 121 | mutex_unlock(&itmt_update_mutex); |
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122 | |
123 | return 0; | |
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124 | } |
125 | ||
126 | /** | |
127 | * sched_clear_itmt_support() - Revoke platform's support of ITMT | |
128 | * | |
129 | * This function is used by the OS to indicate that it has | |
130 | * revoked the platform's support of ITMT feature. | |
131 | * | |
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132 | * It must not be called with cpu hot plug lock |
133 | * held as we need to acquire the lock to rebuild sched domains | |
134 | * later. | |
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135 | */ |
136 | void sched_clear_itmt_support(void) | |
137 | { | |
138 | mutex_lock(&itmt_update_mutex); | |
139 | ||
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140 | if (!sched_itmt_capable) { |
141 | mutex_unlock(&itmt_update_mutex); | |
142 | return; | |
143 | } | |
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144 | sched_itmt_capable = false; |
145 | ||
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146 | if (itmt_sysctl_header) { |
147 | unregister_sysctl_table(itmt_sysctl_header); | |
148 | itmt_sysctl_header = NULL; | |
149 | } | |
150 | ||
151 | if (sysctl_sched_itmt_enabled) { | |
152 | /* disable sched_itmt if we are no longer ITMT capable */ | |
153 | sysctl_sched_itmt_enabled = 0; | |
154 | x86_topology_update = true; | |
155 | rebuild_sched_domains(); | |
156 | } | |
157 | ||
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158 | mutex_unlock(&itmt_update_mutex); |
159 | } | |
160 | ||
161 | int arch_asym_cpu_priority(int cpu) | |
162 | { | |
163 | return per_cpu(sched_core_priority, cpu); | |
164 | } | |
165 | ||
166 | /** | |
167 | * sched_set_itmt_core_prio() - Set CPU priority based on ITMT | |
168 | * @prio: Priority of cpu core | |
169 | * @core_cpu: The cpu number associated with the core | |
170 | * | |
171 | * The pstate driver will find out the max boost frequency | |
172 | * and call this function to set a priority proportional | |
173 | * to the max boost frequency. CPU with higher boost | |
174 | * frequency will receive higher priority. | |
175 | * | |
176 | * No need to rebuild sched domain after updating | |
177 | * the CPU priorities. The sched domains have no | |
178 | * dependency on CPU priorities. | |
179 | */ | |
180 | void sched_set_itmt_core_prio(int prio, int core_cpu) | |
181 | { | |
182 | int cpu, i = 1; | |
183 | ||
184 | for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) { | |
185 | int smt_prio; | |
186 | ||
187 | /* | |
188 | * Ensure that the siblings are moved to the end | |
189 | * of the priority chain and only used when | |
190 | * all other high priority cpus are out of capacity. | |
191 | */ | |
183b8ec3 | 192 | smt_prio = prio * smp_num_siblings / (i * i); |
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193 | per_cpu(sched_core_priority, cpu) = smt_prio; |
194 | i++; | |
195 | } | |
196 | } |