qemu

FORK: QEMU emulator
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cpu-throttle.c (4122B)

      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 
     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_iothread(cpu->halt_cond,
     58                                          sleeptime_ns / SCALE_MS);
     59         } else {
     60             qemu_mutex_unlock_iothread();
     61             g_usleep(sleeptime_ns / SCALE_US);
     62             qemu_mutex_lock_iothread();
     63         }
     64         sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     65     }
     66     qatomic_set(&cpu->throttle_thread_scheduled, 0);
     67 }
     68 
     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 
     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 
    109 void cpu_throttle_stop(void)
    110 {
    111     qatomic_set(&throttle_percentage, 0);
    112 }
    113 
    114 bool cpu_throttle_active(void)
    115 {
    116     return (cpu_throttle_get_percentage() != 0);
    117 }
    118 
    119 int cpu_throttle_get_percentage(void)
    120 {
    121     return qatomic_read(&throttle_percentage);
    122 }
    123 
    124 void cpu_throttle_init(void)
    125 {
    126     throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
    127                                   cpu_throttle_timer_tick, NULL);
    128 }