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7c754c787e
The name "iothread" is overloaded. Use the term Big QEMU Lock (BQL) instead, it is already widely used and unambiguous. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Cédric Le Goater <clg@kaod.org> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Paul Durrant <paul@xen.org> Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com> Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com> Message-id: 20240102153529.486531-4-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
129 lines
4.0 KiB
C
129 lines
4.0 KiB
C
/*
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* QEMU System Emulator
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu/osdep.h"
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#include "qemu/thread.h"
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#include "hw/core/cpu.h"
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#include "qemu/main-loop.h"
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#include "sysemu/cpus.h"
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#include "sysemu/cpu-throttle.h"
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/* vcpu throttling controls */
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static QEMUTimer *throttle_timer;
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static unsigned int throttle_percentage;
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#define CPU_THROTTLE_PCT_MIN 1
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#define CPU_THROTTLE_PCT_MAX 99
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#define CPU_THROTTLE_TIMESLICE_NS 10000000
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static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque)
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{
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double pct;
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double throttle_ratio;
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int64_t sleeptime_ns, endtime_ns;
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if (!cpu_throttle_get_percentage()) {
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return;
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}
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pct = (double)cpu_throttle_get_percentage() / 100;
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throttle_ratio = pct / (1 - pct);
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/* Add 1ns to fix double's rounding error (like 0.9999999...) */
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sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS + 1);
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endtime_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns;
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while (sleeptime_ns > 0 && !cpu->stop) {
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if (sleeptime_ns > SCALE_MS) {
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qemu_cond_timedwait_bql(cpu->halt_cond,
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sleeptime_ns / SCALE_MS);
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} else {
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bql_unlock();
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g_usleep(sleeptime_ns / SCALE_US);
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bql_lock();
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}
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sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
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}
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qatomic_set(&cpu->throttle_thread_scheduled, 0);
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}
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static void cpu_throttle_timer_tick(void *opaque)
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{
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CPUState *cpu;
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double pct;
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/* Stop the timer if needed */
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if (!cpu_throttle_get_percentage()) {
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return;
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}
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CPU_FOREACH(cpu) {
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if (!qatomic_xchg(&cpu->throttle_thread_scheduled, 1)) {
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async_run_on_cpu(cpu, cpu_throttle_thread,
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RUN_ON_CPU_NULL);
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}
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}
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pct = (double)cpu_throttle_get_percentage() / 100;
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timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
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CPU_THROTTLE_TIMESLICE_NS / (1 - pct));
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}
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void cpu_throttle_set(int new_throttle_pct)
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{
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/*
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* boolean to store whether throttle is already active or not,
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* before modifying throttle_percentage
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*/
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bool throttle_active = cpu_throttle_active();
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/* Ensure throttle percentage is within valid range */
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new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX);
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new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN);
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qatomic_set(&throttle_percentage, new_throttle_pct);
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if (!throttle_active) {
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cpu_throttle_timer_tick(NULL);
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}
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}
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void cpu_throttle_stop(void)
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{
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qatomic_set(&throttle_percentage, 0);
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}
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bool cpu_throttle_active(void)
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{
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return (cpu_throttle_get_percentage() != 0);
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}
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int cpu_throttle_get_percentage(void)
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{
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return qatomic_read(&throttle_percentage);
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}
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void cpu_throttle_init(void)
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{
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throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
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cpu_throttle_timer_tick, NULL);
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}
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