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3e51f33f PZ |
1 | /* |
2 | * sched_clock for unstable cpu clocks | |
3 | * | |
4 | * Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> | |
5 | * | |
c300ba25 SR |
6 | * Updates and enhancements: |
7 | * Copyright (C) 2008 Red Hat, Inc. Steven Rostedt <srostedt@redhat.com> | |
8 | * | |
3e51f33f PZ |
9 | * Based on code by: |
10 | * Ingo Molnar <mingo@redhat.com> | |
11 | * Guillaume Chazarain <guichaz@gmail.com> | |
12 | * | |
13 | * Create a semi stable clock from a mixture of other events, including: | |
14 | * - gtod | |
3e51f33f PZ |
15 | * - sched_clock() |
16 | * - explicit idle events | |
17 | * | |
18 | * We use gtod as base and the unstable clock deltas. The deltas are filtered, | |
354879bb | 19 | * making it monotonic and keeping it within an expected window. |
3e51f33f PZ |
20 | * |
21 | * Furthermore, explicit sleep and wakeup hooks allow us to account for time | |
22 | * that is otherwise invisible (TSC gets stopped). | |
23 | * | |
24 | * The clock: sched_clock_cpu() is monotonic per cpu, and should be somewhat | |
354879bb | 25 | * consistent between cpus (never more than 2 jiffies difference). |
3e51f33f PZ |
26 | */ |
27 | #include <linux/sched.h> | |
28 | #include <linux/percpu.h> | |
29 | #include <linux/spinlock.h> | |
30 | #include <linux/ktime.h> | |
31 | #include <linux/module.h> | |
32 | ||
2c3d103b HD |
33 | /* |
34 | * Scheduler clock - returns current time in nanosec units. | |
35 | * This is default implementation. | |
36 | * Architectures and sub-architectures can override this. | |
37 | */ | |
38 | unsigned long long __attribute__((weak)) sched_clock(void) | |
39 | { | |
40 | return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); | |
41 | } | |
3e51f33f | 42 | |
c1955a3d PZ |
43 | static __read_mostly int sched_clock_running; |
44 | ||
3e51f33f PZ |
45 | #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK |
46 | ||
47 | struct sched_clock_data { | |
48 | /* | |
49 | * Raw spinlock - this is a special case: this might be called | |
50 | * from within instrumentation code so we dont want to do any | |
51 | * instrumentation ourselves. | |
52 | */ | |
53 | raw_spinlock_t lock; | |
54 | ||
3e51f33f PZ |
55 | u64 tick_raw; |
56 | u64 tick_gtod; | |
57 | u64 clock; | |
58 | }; | |
59 | ||
60 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data); | |
61 | ||
62 | static inline struct sched_clock_data *this_scd(void) | |
63 | { | |
64 | return &__get_cpu_var(sched_clock_data); | |
65 | } | |
66 | ||
67 | static inline struct sched_clock_data *cpu_sdc(int cpu) | |
68 | { | |
69 | return &per_cpu(sched_clock_data, cpu); | |
70 | } | |
71 | ||
72 | void sched_clock_init(void) | |
73 | { | |
74 | u64 ktime_now = ktime_to_ns(ktime_get()); | |
3e51f33f PZ |
75 | int cpu; |
76 | ||
77 | for_each_possible_cpu(cpu) { | |
78 | struct sched_clock_data *scd = cpu_sdc(cpu); | |
79 | ||
80 | scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; | |
a381759d | 81 | scd->tick_raw = 0; |
3e51f33f PZ |
82 | scd->tick_gtod = ktime_now; |
83 | scd->clock = ktime_now; | |
84 | } | |
a381759d PZ |
85 | |
86 | sched_clock_running = 1; | |
3e51f33f PZ |
87 | } |
88 | ||
354879bb PZ |
89 | /* |
90 | * min,max except they take wrapping into account | |
91 | */ | |
92 | ||
93 | static inline u64 wrap_min(u64 x, u64 y) | |
94 | { | |
95 | return (s64)(x - y) < 0 ? x : y; | |
96 | } | |
97 | ||
98 | static inline u64 wrap_max(u64 x, u64 y) | |
99 | { | |
100 | return (s64)(x - y) > 0 ? x : y; | |
101 | } | |
102 | ||
3e51f33f PZ |
103 | /* |
104 | * update the percpu scd from the raw @now value | |
105 | * | |
106 | * - filter out backward motion | |
354879bb | 107 | * - use the GTOD tick value to create a window to filter crazy TSC values |
3e51f33f | 108 | */ |
56b90612 | 109 | static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now) |
3e51f33f | 110 | { |
18e4e36c | 111 | s64 delta = now - scd->tick_raw; |
354879bb | 112 | u64 clock, min_clock, max_clock; |
3e51f33f PZ |
113 | |
114 | WARN_ON_ONCE(!irqs_disabled()); | |
3e51f33f | 115 | |
354879bb PZ |
116 | if (unlikely(delta < 0)) |
117 | delta = 0; | |
3e51f33f | 118 | |
354879bb PZ |
119 | /* |
120 | * scd->clock = clamp(scd->tick_gtod + delta, | |
ca7e716c LT |
121 | * max(scd->tick_gtod, scd->clock), |
122 | * scd->tick_gtod + TICK_NSEC); | |
354879bb | 123 | */ |
3e51f33f | 124 | |
354879bb PZ |
125 | clock = scd->tick_gtod + delta; |
126 | min_clock = wrap_max(scd->tick_gtod, scd->clock); | |
1c5745aa | 127 | max_clock = wrap_max(scd->clock, scd->tick_gtod + TICK_NSEC); |
3e51f33f | 128 | |
354879bb PZ |
129 | clock = wrap_max(clock, min_clock); |
130 | clock = wrap_min(clock, max_clock); | |
3e51f33f | 131 | |
e4e4e534 | 132 | scd->clock = clock; |
56b90612 | 133 | |
354879bb | 134 | return scd->clock; |
3e51f33f PZ |
135 | } |
136 | ||
137 | static void lock_double_clock(struct sched_clock_data *data1, | |
138 | struct sched_clock_data *data2) | |
139 | { | |
140 | if (data1 < data2) { | |
141 | __raw_spin_lock(&data1->lock); | |
142 | __raw_spin_lock(&data2->lock); | |
143 | } else { | |
144 | __raw_spin_lock(&data2->lock); | |
145 | __raw_spin_lock(&data1->lock); | |
146 | } | |
147 | } | |
148 | ||
149 | u64 sched_clock_cpu(int cpu) | |
150 | { | |
151 | struct sched_clock_data *scd = cpu_sdc(cpu); | |
4a273f20 | 152 | u64 now, clock, this_clock, remote_clock; |
3e51f33f | 153 | |
a381759d PZ |
154 | if (unlikely(!sched_clock_running)) |
155 | return 0ull; | |
156 | ||
3e51f33f PZ |
157 | WARN_ON_ONCE(!irqs_disabled()); |
158 | now = sched_clock(); | |
159 | ||
160 | if (cpu != raw_smp_processor_id()) { | |
3e51f33f PZ |
161 | struct sched_clock_data *my_scd = this_scd(); |
162 | ||
163 | lock_double_clock(scd, my_scd); | |
164 | ||
4a273f20 IM |
165 | this_clock = __update_sched_clock(my_scd, now); |
166 | remote_clock = scd->clock; | |
167 | ||
168 | /* | |
169 | * Use the opportunity that we have both locks | |
170 | * taken to couple the two clocks: we take the | |
171 | * larger time as the latest time for both | |
172 | * runqueues. (this creates monotonic movement) | |
173 | */ | |
354879bb | 174 | if (likely((s64)(remote_clock - this_clock) < 0)) { |
4a273f20 IM |
175 | clock = this_clock; |
176 | scd->clock = clock; | |
177 | } else { | |
178 | /* | |
179 | * Should be rare, but possible: | |
180 | */ | |
181 | clock = remote_clock; | |
182 | my_scd->clock = remote_clock; | |
183 | } | |
3e51f33f PZ |
184 | |
185 | __raw_spin_unlock(&my_scd->lock); | |
186 | } else { | |
187 | __raw_spin_lock(&scd->lock); | |
4a273f20 | 188 | clock = __update_sched_clock(scd, now); |
3e51f33f PZ |
189 | } |
190 | ||
e4e4e534 IM |
191 | __raw_spin_unlock(&scd->lock); |
192 | ||
3e51f33f PZ |
193 | return clock; |
194 | } | |
195 | ||
196 | void sched_clock_tick(void) | |
197 | { | |
198 | struct sched_clock_data *scd = this_scd(); | |
199 | u64 now, now_gtod; | |
200 | ||
a381759d PZ |
201 | if (unlikely(!sched_clock_running)) |
202 | return; | |
203 | ||
3e51f33f PZ |
204 | WARN_ON_ONCE(!irqs_disabled()); |
205 | ||
3e51f33f | 206 | now_gtod = ktime_to_ns(ktime_get()); |
a83bc47c | 207 | now = sched_clock(); |
3e51f33f PZ |
208 | |
209 | __raw_spin_lock(&scd->lock); | |
3e51f33f PZ |
210 | scd->tick_raw = now; |
211 | scd->tick_gtod = now_gtod; | |
354879bb | 212 | __update_sched_clock(scd, now); |
3e51f33f PZ |
213 | __raw_spin_unlock(&scd->lock); |
214 | } | |
215 | ||
216 | /* | |
217 | * We are going deep-idle (irqs are disabled): | |
218 | */ | |
219 | void sched_clock_idle_sleep_event(void) | |
220 | { | |
221 | sched_clock_cpu(smp_processor_id()); | |
222 | } | |
223 | EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); | |
224 | ||
225 | /* | |
226 | * We just idled delta nanoseconds (called with irqs disabled): | |
227 | */ | |
228 | void sched_clock_idle_wakeup_event(u64 delta_ns) | |
229 | { | |
1c5745aa TG |
230 | if (timekeeping_suspended) |
231 | return; | |
232 | ||
354879bb | 233 | sched_clock_tick(); |
3e51f33f PZ |
234 | touch_softlockup_watchdog(); |
235 | } | |
236 | EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); | |
237 | ||
c1955a3d PZ |
238 | #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ |
239 | ||
240 | void sched_clock_init(void) | |
241 | { | |
242 | sched_clock_running = 1; | |
243 | } | |
244 | ||
245 | u64 sched_clock_cpu(int cpu) | |
246 | { | |
247 | if (unlikely(!sched_clock_running)) | |
248 | return 0; | |
249 | ||
250 | return sched_clock(); | |
251 | } | |
252 | ||
3e51f33f PZ |
253 | #endif |
254 | ||
76a2a6ee PZ |
255 | unsigned long long cpu_clock(int cpu) |
256 | { | |
257 | unsigned long long clock; | |
258 | unsigned long flags; | |
259 | ||
2d452c9b | 260 | local_irq_save(flags); |
76a2a6ee | 261 | clock = sched_clock_cpu(cpu); |
2d452c9b | 262 | local_irq_restore(flags); |
76a2a6ee PZ |
263 | |
264 | return clock; | |
265 | } | |
4c9fe8ad | 266 | EXPORT_SYMBOL_GPL(cpu_clock); |