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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) |
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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 | ||
80 | static struct ctl_table itmt_root_table[] = { | |
81 | { | |
82 | .procname = "kernel", | |
83 | .mode = 0555, | |
84 | .child = itmt_kern_table, | |
85 | }, | |
86 | {} | |
87 | }; | |
88 | ||
89 | static struct ctl_table_header *itmt_sysctl_header; | |
90 | ||
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91 | /** |
92 | * sched_set_itmt_support() - Indicate platform supports ITMT | |
93 | * | |
94 | * This function is used by the OS to indicate to scheduler that the platform | |
95 | * is capable of supporting the ITMT feature. | |
96 | * | |
97 | * The current scheme has the pstate driver detects if the system | |
98 | * is ITMT capable and call sched_set_itmt_support. | |
99 | * | |
100 | * This must be done only after sched_set_itmt_core_prio | |
101 | * has been called to set the cpus' priorities. | |
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102 | * It must not be called with cpu hot plug lock |
103 | * held as we need to acquire the lock to rebuild sched domains | |
104 | * later. | |
105 | * | |
106 | * Return: 0 on success | |
5e76b2ab | 107 | */ |
f9793e34 | 108 | int sched_set_itmt_support(void) |
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109 | { |
110 | mutex_lock(&itmt_update_mutex); | |
111 | ||
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112 | if (sched_itmt_capable) { |
113 | mutex_unlock(&itmt_update_mutex); | |
114 | return 0; | |
115 | } | |
116 | ||
117 | itmt_sysctl_header = register_sysctl_table(itmt_root_table); | |
118 | if (!itmt_sysctl_header) { | |
119 | mutex_unlock(&itmt_update_mutex); | |
120 | return -ENOMEM; | |
121 | } | |
122 | ||
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123 | sched_itmt_capable = true; |
124 | ||
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125 | sysctl_sched_itmt_enabled = 1; |
126 | ||
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127 | x86_topology_update = true; |
128 | rebuild_sched_domains(); | |
f9793e34 | 129 | |
5e76b2ab | 130 | mutex_unlock(&itmt_update_mutex); |
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131 | |
132 | return 0; | |
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133 | } |
134 | ||
135 | /** | |
136 | * sched_clear_itmt_support() - Revoke platform's support of ITMT | |
137 | * | |
138 | * This function is used by the OS to indicate that it has | |
139 | * revoked the platform's support of ITMT feature. | |
140 | * | |
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141 | * It must not be called with cpu hot plug lock |
142 | * held as we need to acquire the lock to rebuild sched domains | |
143 | * later. | |
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144 | */ |
145 | void sched_clear_itmt_support(void) | |
146 | { | |
147 | mutex_lock(&itmt_update_mutex); | |
148 | ||
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149 | if (!sched_itmt_capable) { |
150 | mutex_unlock(&itmt_update_mutex); | |
151 | return; | |
152 | } | |
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153 | sched_itmt_capable = false; |
154 | ||
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155 | if (itmt_sysctl_header) { |
156 | unregister_sysctl_table(itmt_sysctl_header); | |
157 | itmt_sysctl_header = NULL; | |
158 | } | |
159 | ||
160 | if (sysctl_sched_itmt_enabled) { | |
161 | /* disable sched_itmt if we are no longer ITMT capable */ | |
162 | sysctl_sched_itmt_enabled = 0; | |
163 | x86_topology_update = true; | |
164 | rebuild_sched_domains(); | |
165 | } | |
166 | ||
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167 | mutex_unlock(&itmt_update_mutex); |
168 | } | |
169 | ||
170 | int arch_asym_cpu_priority(int cpu) | |
171 | { | |
172 | return per_cpu(sched_core_priority, cpu); | |
173 | } | |
174 | ||
175 | /** | |
176 | * sched_set_itmt_core_prio() - Set CPU priority based on ITMT | |
177 | * @prio: Priority of cpu core | |
178 | * @core_cpu: The cpu number associated with the core | |
179 | * | |
180 | * The pstate driver will find out the max boost frequency | |
181 | * and call this function to set a priority proportional | |
182 | * to the max boost frequency. CPU with higher boost | |
183 | * frequency will receive higher priority. | |
184 | * | |
185 | * No need to rebuild sched domain after updating | |
186 | * the CPU priorities. The sched domains have no | |
187 | * dependency on CPU priorities. | |
188 | */ | |
189 | void sched_set_itmt_core_prio(int prio, int core_cpu) | |
190 | { | |
191 | int cpu, i = 1; | |
192 | ||
193 | for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) { | |
194 | int smt_prio; | |
195 | ||
196 | /* | |
197 | * Ensure that the siblings are moved to the end | |
198 | * of the priority chain and only used when | |
199 | * all other high priority cpus are out of capacity. | |
200 | */ | |
201 | smt_prio = prio * smp_num_siblings / i; | |
202 | per_cpu(sched_core_priority, cpu) = smt_prio; | |
203 | i++; | |
204 | } | |
205 | } |