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5e76b2ab TC |
1 | /* |
2 | * itmt.c: Support Intel Turbo Boost Max Technology 3.0 | |
3 | * | |
4 | * (C) Copyright 2016 Intel Corporation | |
5 | * Author: Tim Chen <tim.c.chen@linux.intel.com> | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or | |
8 | * modify it under the terms of the GNU General Public License | |
9 | * as published by the Free Software Foundation; version 2 | |
10 | * of the License. | |
11 | * | |
12 | * On platforms supporting Intel Turbo Boost Max Technology 3.0, (ITMT), | |
13 | * the maximum turbo frequencies of some cores in a CPU package may be | |
14 | * higher than for the other cores in the same package. In that case, | |
15 | * better performance can be achieved by making the scheduler prefer | |
16 | * to run tasks on the CPUs with higher max turbo frequencies. | |
17 | * | |
18 | * This file provides functions and data structures for enabling the | |
19 | * scheduler to favor scheduling on cores can be boosted to a higher | |
20 | * frequency under ITMT. | |
21 | */ | |
22 | ||
23 | #include <linux/sched.h> | |
24 | #include <linux/cpumask.h> | |
25 | #include <linux/cpuset.h> | |
a293b395 | 26 | #include <linux/mutex.h> |
5e76b2ab TC |
27 | #include <linux/sysctl.h> |
28 | #include <linux/nodemask.h> | |
29 | ||
30 | static DEFINE_MUTEX(itmt_update_mutex); | |
31 | DEFINE_PER_CPU_READ_MOSTLY(int, sched_core_priority); | |
32 | ||
33 | /* Boolean to track if system has ITMT capabilities */ | |
34 | static bool __read_mostly sched_itmt_capable; | |
35 | ||
f9793e34 TC |
36 | /* |
37 | * Boolean to control whether we want to move processes to cpu capable | |
38 | * of higher turbo frequency for cpus supporting Intel Turbo Boost Max | |
39 | * Technology 3.0. | |
40 | * | |
41 | * It can be set via /proc/sys/kernel/sched_itmt_enabled | |
42 | */ | |
43 | unsigned int __read_mostly sysctl_sched_itmt_enabled; | |
44 | ||
45 | static int sched_itmt_update_handler(struct ctl_table *table, int write, | |
46 | void __user *buffer, size_t *lenp, | |
47 | loff_t *ppos) | |
48 | { | |
49 | unsigned int old_sysctl; | |
50 | int ret; | |
51 | ||
52 | mutex_lock(&itmt_update_mutex); | |
53 | ||
54 | if (!sched_itmt_capable) { | |
55 | mutex_unlock(&itmt_update_mutex); | |
56 | return -EINVAL; | |
57 | } | |
58 | ||
59 | old_sysctl = sysctl_sched_itmt_enabled; | |
60 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
61 | ||
62 | if (!ret && write && old_sysctl != sysctl_sched_itmt_enabled) { | |
63 | x86_topology_update = true; | |
64 | rebuild_sched_domains(); | |
65 | } | |
66 | ||
67 | mutex_unlock(&itmt_update_mutex); | |
68 | ||
69 | return ret; | |
70 | } | |
71 | ||
72 | static unsigned int zero; | |
73 | static unsigned int one = 1; | |
74 | static struct ctl_table itmt_kern_table[] = { | |
75 | { | |
76 | .procname = "sched_itmt_enabled", | |
77 | .data = &sysctl_sched_itmt_enabled, | |
78 | .maxlen = sizeof(unsigned int), | |
79 | .mode = 0644, | |
80 | .proc_handler = sched_itmt_update_handler, | |
81 | .extra1 = &zero, | |
82 | .extra2 = &one, | |
83 | }, | |
84 | {} | |
85 | }; | |
86 | ||
87 | static struct ctl_table itmt_root_table[] = { | |
88 | { | |
89 | .procname = "kernel", | |
90 | .mode = 0555, | |
91 | .child = itmt_kern_table, | |
92 | }, | |
93 | {} | |
94 | }; | |
95 | ||
96 | static struct ctl_table_header *itmt_sysctl_header; | |
97 | ||
5e76b2ab TC |
98 | /** |
99 | * sched_set_itmt_support() - Indicate platform supports ITMT | |
100 | * | |
101 | * This function is used by the OS to indicate to scheduler that the platform | |
102 | * is capable of supporting the ITMT feature. | |
103 | * | |
104 | * The current scheme has the pstate driver detects if the system | |
105 | * is ITMT capable and call sched_set_itmt_support. | |
106 | * | |
107 | * This must be done only after sched_set_itmt_core_prio | |
108 | * has been called to set the cpus' priorities. | |
f9793e34 TC |
109 | * It must not be called with cpu hot plug lock |
110 | * held as we need to acquire the lock to rebuild sched domains | |
111 | * later. | |
112 | * | |
113 | * Return: 0 on success | |
5e76b2ab | 114 | */ |
f9793e34 | 115 | int sched_set_itmt_support(void) |
5e76b2ab TC |
116 | { |
117 | mutex_lock(&itmt_update_mutex); | |
118 | ||
f9793e34 TC |
119 | if (sched_itmt_capable) { |
120 | mutex_unlock(&itmt_update_mutex); | |
121 | return 0; | |
122 | } | |
123 | ||
124 | itmt_sysctl_header = register_sysctl_table(itmt_root_table); | |
125 | if (!itmt_sysctl_header) { | |
126 | mutex_unlock(&itmt_update_mutex); | |
127 | return -ENOMEM; | |
128 | } | |
129 | ||
5e76b2ab TC |
130 | sched_itmt_capable = true; |
131 | ||
f9793e34 TC |
132 | sysctl_sched_itmt_enabled = 1; |
133 | ||
02cfdc95 TC |
134 | x86_topology_update = true; |
135 | rebuild_sched_domains(); | |
f9793e34 | 136 | |
5e76b2ab | 137 | mutex_unlock(&itmt_update_mutex); |
f9793e34 TC |
138 | |
139 | return 0; | |
5e76b2ab TC |
140 | } |
141 | ||
142 | /** | |
143 | * sched_clear_itmt_support() - Revoke platform's support of ITMT | |
144 | * | |
145 | * This function is used by the OS to indicate that it has | |
146 | * revoked the platform's support of ITMT feature. | |
147 | * | |
f9793e34 TC |
148 | * It must not be called with cpu hot plug lock |
149 | * held as we need to acquire the lock to rebuild sched domains | |
150 | * later. | |
5e76b2ab TC |
151 | */ |
152 | void sched_clear_itmt_support(void) | |
153 | { | |
154 | mutex_lock(&itmt_update_mutex); | |
155 | ||
f9793e34 TC |
156 | if (!sched_itmt_capable) { |
157 | mutex_unlock(&itmt_update_mutex); | |
158 | return; | |
159 | } | |
5e76b2ab TC |
160 | sched_itmt_capable = false; |
161 | ||
f9793e34 TC |
162 | if (itmt_sysctl_header) { |
163 | unregister_sysctl_table(itmt_sysctl_header); | |
164 | itmt_sysctl_header = NULL; | |
165 | } | |
166 | ||
167 | if (sysctl_sched_itmt_enabled) { | |
168 | /* disable sched_itmt if we are no longer ITMT capable */ | |
169 | sysctl_sched_itmt_enabled = 0; | |
170 | x86_topology_update = true; | |
171 | rebuild_sched_domains(); | |
172 | } | |
173 | ||
5e76b2ab TC |
174 | mutex_unlock(&itmt_update_mutex); |
175 | } | |
176 | ||
177 | int arch_asym_cpu_priority(int cpu) | |
178 | { | |
179 | return per_cpu(sched_core_priority, cpu); | |
180 | } | |
181 | ||
182 | /** | |
183 | * sched_set_itmt_core_prio() - Set CPU priority based on ITMT | |
184 | * @prio: Priority of cpu core | |
185 | * @core_cpu: The cpu number associated with the core | |
186 | * | |
187 | * The pstate driver will find out the max boost frequency | |
188 | * and call this function to set a priority proportional | |
189 | * to the max boost frequency. CPU with higher boost | |
190 | * frequency will receive higher priority. | |
191 | * | |
192 | * No need to rebuild sched domain after updating | |
193 | * the CPU priorities. The sched domains have no | |
194 | * dependency on CPU priorities. | |
195 | */ | |
196 | void sched_set_itmt_core_prio(int prio, int core_cpu) | |
197 | { | |
198 | int cpu, i = 1; | |
199 | ||
200 | for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) { | |
201 | int smt_prio; | |
202 | ||
203 | /* | |
204 | * Ensure that the siblings are moved to the end | |
205 | * of the priority chain and only used when | |
206 | * all other high priority cpus are out of capacity. | |
207 | */ | |
208 | smt_prio = prio * smp_num_siblings / i; | |
209 | per_cpu(sched_core_priority, cpu) = smt_prio; | |
210 | i++; | |
211 | } | |
212 | } |