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/*
* QEMU System Emulator
*
* Copyright (c) 2003-2008 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qemu/thread.h"
#include "hw/core/cpu.h"
#include "qemu/main-loop.h"
#include "system/cpus.h"
#include "system/cpu-throttle.h"
#include "migration.h"
#include "migration-stats.h"
#include "trace.h"
/* vcpu throttling controls */
static QEMUTimer *throttle_timer, *throttle_dirty_sync_timer;
static unsigned int throttle_percentage;
static bool throttle_dirty_sync_timer_active;
static uint64_t throttle_dirty_sync_count_prev;
#define CPU_THROTTLE_PCT_MIN 1
#define CPU_THROTTLE_PCT_MAX 99
#define CPU_THROTTLE_TIMESLICE_NS 10000000
/* Making sure RAMBlock dirty bitmap is synchronized every five seconds */
#define CPU_THROTTLE_DIRTY_SYNC_TIMESLICE_MS 5000
static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque)
{
double pct;
double throttle_ratio;
int64_t sleeptime_ns, endtime_ns;
if (!cpu_throttle_get_percentage()) {
return;
}
pct = (double)cpu_throttle_get_percentage() / 100;
throttle_ratio = pct / (1 - pct);
/* Add 1ns to fix double's rounding error (like 0.9999999...) */
sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS + 1);
endtime_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns;
while (sleeptime_ns > 0 && !cpu->stop) {
if (sleeptime_ns > SCALE_MS) {
qemu_cond_timedwait_bql(cpu->halt_cond,
sleeptime_ns / SCALE_MS);
} else {
bql_unlock();
g_usleep(sleeptime_ns / SCALE_US);
bql_lock();
}
sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
}
qatomic_set(&cpu->throttle_thread_scheduled, 0);
}
static void cpu_throttle_timer_tick(void *opaque)
{
CPUState *cpu;
double pct;
/* Stop the timer if needed */
if (!cpu_throttle_get_percentage()) {
return;
}
CPU_FOREACH(cpu) {
if (!qatomic_xchg(&cpu->throttle_thread_scheduled, 1)) {
async_run_on_cpu(cpu, cpu_throttle_thread,
RUN_ON_CPU_NULL);
}
}
pct = (double)cpu_throttle_get_percentage() / 100;
timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
CPU_THROTTLE_TIMESLICE_NS / (1 - pct));
}
void cpu_throttle_set(int new_throttle_pct)
{
/*
* boolean to store whether throttle is already active or not,
* before modifying throttle_percentage
*/
bool throttle_active = cpu_throttle_active();
trace_cpu_throttle_set(new_throttle_pct);
/* Ensure throttle percentage is within valid range */
new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX);
new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN);
qatomic_set(&throttle_percentage, new_throttle_pct);
if (!throttle_active) {
cpu_throttle_timer_tick(NULL);
}
}
void cpu_throttle_stop(void)
{
qatomic_set(&throttle_percentage, 0);
cpu_throttle_dirty_sync_timer(false);
}
bool cpu_throttle_active(void)
{
return (cpu_throttle_get_percentage() != 0);
}
int cpu_throttle_get_percentage(void)
{
return qatomic_read(&throttle_percentage);
}
void cpu_throttle_dirty_sync_timer_tick(void *opaque)
{
uint64_t sync_cnt = stat64_get(&mig_stats.dirty_sync_count);
/*
* The first iteration copies all memory anyhow and has no
* effect on guest performance, therefore omit it to avoid
* paying extra for the sync penalty.
*/
if (sync_cnt <= 1) {
goto end;
}
if (sync_cnt == throttle_dirty_sync_count_prev) {
trace_cpu_throttle_dirty_sync();
WITH_RCU_READ_LOCK_GUARD() {
migration_bitmap_sync_precopy(false);
}
}
end:
throttle_dirty_sync_count_prev = stat64_get(&mig_stats.dirty_sync_count);
timer_mod(throttle_dirty_sync_timer,
qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) +
CPU_THROTTLE_DIRTY_SYNC_TIMESLICE_MS);
}
static bool cpu_throttle_dirty_sync_active(void)
{
return qatomic_read(&throttle_dirty_sync_timer_active);
}
void cpu_throttle_dirty_sync_timer(bool enable)
{
assert(throttle_dirty_sync_timer);
if (enable) {
if (!cpu_throttle_dirty_sync_active()) {
/*
* Always reset the dirty sync count cache, in case migration
* was cancelled once.
*/
throttle_dirty_sync_count_prev = 0;
timer_mod(throttle_dirty_sync_timer,
qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) +
CPU_THROTTLE_DIRTY_SYNC_TIMESLICE_MS);
qatomic_set(&throttle_dirty_sync_timer_active, 1);
}
} else {
if (cpu_throttle_dirty_sync_active()) {
timer_del(throttle_dirty_sync_timer);
qatomic_set(&throttle_dirty_sync_timer_active, 0);
}
}
}
void cpu_throttle_init(void)
{
throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
cpu_throttle_timer_tick, NULL);
throttle_dirty_sync_timer =
timer_new_ms(QEMU_CLOCK_VIRTUAL_RT,
cpu_throttle_dirty_sync_timer_tick, NULL);
}
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