1 /*
2 * QEMU System Emulator
3 *
4 * Copyright (c) 2003-2008 Fabrice Bellard
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24
25 #include "qemu/osdep.h"
26 #include "qemu/thread.h"
27 #include "hw/core/cpu.h"
28 #include "qemu/main-loop.h"
29 #include "sysemu/cpus.h"
30 #include "sysemu/cpu-throttle.h"
31
32 /* vcpu throttling controls */
33 static QEMUTimer *throttle_timer;
34 static unsigned int throttle_percentage;
35
36 #define CPU_THROTTLE_PCT_MIN 1
37 #define CPU_THROTTLE_PCT_MAX 99
38 #define CPU_THROTTLE_TIMESLICE_NS 10000000
39
cpu_throttle_thread(CPUState * cpu,run_on_cpu_data opaque)40 static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque)
41 {
42 double pct;
43 double throttle_ratio;
44 int64_t sleeptime_ns, endtime_ns;
45
46 if (!cpu_throttle_get_percentage()) {
47 return;
48 }
49
50 pct = (double)cpu_throttle_get_percentage() / 100;
51 throttle_ratio = pct / (1 - pct);
52 /* Add 1ns to fix double's rounding error (like 0.9999999...) */
53 sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS + 1);
54 endtime_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns;
55 while (sleeptime_ns > 0 && !cpu->stop) {
56 if (sleeptime_ns > SCALE_MS) {
57 qemu_cond_timedwait_bql(cpu->halt_cond,
58 sleeptime_ns / SCALE_MS);
59 } else {
60 bql_unlock();
61 g_usleep(sleeptime_ns / SCALE_US);
62 bql_lock();
63 }
64 sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
65 }
66 qatomic_set(&cpu->throttle_thread_scheduled, 0);
67 }
68
cpu_throttle_timer_tick(void * opaque)69 static void cpu_throttle_timer_tick(void *opaque)
70 {
71 CPUState *cpu;
72 double pct;
73
74 /* Stop the timer if needed */
75 if (!cpu_throttle_get_percentage()) {
76 return;
77 }
78 CPU_FOREACH(cpu) {
79 if (!qatomic_xchg(&cpu->throttle_thread_scheduled, 1)) {
80 async_run_on_cpu(cpu, cpu_throttle_thread,
81 RUN_ON_CPU_NULL);
82 }
83 }
84
85 pct = (double)cpu_throttle_get_percentage() / 100;
86 timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
87 CPU_THROTTLE_TIMESLICE_NS / (1 - pct));
88 }
89
cpu_throttle_set(int new_throttle_pct)90 void cpu_throttle_set(int new_throttle_pct)
91 {
92 /*
93 * boolean to store whether throttle is already active or not,
94 * before modifying throttle_percentage
95 */
96 bool throttle_active = cpu_throttle_active();
97
98 /* Ensure throttle percentage is within valid range */
99 new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX);
100 new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN);
101
102 qatomic_set(&throttle_percentage, new_throttle_pct);
103
104 if (!throttle_active) {
105 cpu_throttle_timer_tick(NULL);
106 }
107 }
108
cpu_throttle_stop(void)109 void cpu_throttle_stop(void)
110 {
111 qatomic_set(&throttle_percentage, 0);
112 }
113
cpu_throttle_active(void)114 bool cpu_throttle_active(void)
115 {
116 return (cpu_throttle_get_percentage() != 0);
117 }
118
cpu_throttle_get_percentage(void)119 int cpu_throttle_get_percentage(void)
120 {
121 return qatomic_read(&throttle_percentage);
122 }
123
cpu_throttle_init(void)124 void cpu_throttle_init(void)
125 {
126 throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
127 cpu_throttle_timer_tick, NULL);
128 }
129