Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20210921' into staging
[qemu.git] / softmmu / cpu-throttle.c
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-common.h"
27 #include "qemu/thread.h"
28 #include "hw/core/cpu.h"
29 #include "qemu/main-loop.h"
30 #include "sysemu/cpus.h"
31 #include "sysemu/cpu-throttle.h"
32
33 /* vcpu throttling controls */
34 static QEMUTimer *throttle_timer;
35 static unsigned int throttle_percentage;
36
37 #define CPU_THROTTLE_PCT_MIN 1
38 #define CPU_THROTTLE_PCT_MAX 99
39 #define CPU_THROTTLE_TIMESLICE_NS 10000000
40
41 static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque)
42 {
43 double pct;
44 double throttle_ratio;
45 int64_t sleeptime_ns, endtime_ns;
46
47 if (!cpu_throttle_get_percentage()) {
48 return;
49 }
50
51 pct = (double)cpu_throttle_get_percentage() / 100;
52 throttle_ratio = pct / (1 - pct);
53 /* Add 1ns to fix double's rounding error (like 0.9999999...) */
54 sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS + 1);
55 endtime_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns;
56 while (sleeptime_ns > 0 && !cpu->stop) {
57 if (sleeptime_ns > SCALE_MS) {
58 qemu_cond_timedwait_iothread(cpu->halt_cond,
59 sleeptime_ns / SCALE_MS);
60 } else {
61 qemu_mutex_unlock_iothread();
62 g_usleep(sleeptime_ns / SCALE_US);
63 qemu_mutex_lock_iothread();
64 }
65 sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
66 }
67 qatomic_set(&cpu->throttle_thread_scheduled, 0);
68 }
69
70 static void cpu_throttle_timer_tick(void *opaque)
71 {
72 CPUState *cpu;
73 double pct;
74
75 /* Stop the timer if needed */
76 if (!cpu_throttle_get_percentage()) {
77 return;
78 }
79 CPU_FOREACH(cpu) {
80 if (!qatomic_xchg(&cpu->throttle_thread_scheduled, 1)) {
81 async_run_on_cpu(cpu, cpu_throttle_thread,
82 RUN_ON_CPU_NULL);
83 }
84 }
85
86 pct = (double)cpu_throttle_get_percentage() / 100;
87 timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
88 CPU_THROTTLE_TIMESLICE_NS / (1 - pct));
89 }
90
91 void cpu_throttle_set(int new_throttle_pct)
92 {
93 /*
94 * boolean to store whether throttle is already active or not,
95 * before modifying throttle_percentage
96 */
97 bool throttle_active = cpu_throttle_active();
98
99 /* Ensure throttle percentage is within valid range */
100 new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX);
101 new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN);
102
103 qatomic_set(&throttle_percentage, new_throttle_pct);
104
105 if (!throttle_active) {
106 cpu_throttle_timer_tick(NULL);
107 }
108 }
109
110 void cpu_throttle_stop(void)
111 {
112 qatomic_set(&throttle_percentage, 0);
113 }
114
115 bool cpu_throttle_active(void)
116 {
117 return (cpu_throttle_get_percentage() != 0);
118 }
119
120 int cpu_throttle_get_percentage(void)
121 {
122 return qatomic_read(&throttle_percentage);
123 }
124
125 void cpu_throttle_init(void)
126 {
127 throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
128 cpu_throttle_timer_tick, NULL);
129 }