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authorStefan Hajnoczi <stefanha@redhat.com>2023-10-09 10:11:17 -0400
committerStefan Hajnoczi <stefanha@redhat.com>2023-10-09 10:11:18 -0400
commit1527c6b6fa6c6775523287e33f78b41afc7ba46c (patch)
treee245ed1f0f1856b800b391e22da9d09b21950540 /system/cpu-throttle.c
parentf7294103560260ff09ffdf316cf6ba6d4e368d85 (diff)
parent912eef205ae9ccfd477c343a51a7c2dcfae2ba43 (diff)
downloadfocaccia-qemu-1527c6b6fa6c6775523287e33f78b41afc7ba46c.tar.gz
focaccia-qemu-1527c6b6fa6c6775523287e33f78b41afc7ba46c.zip
Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging
* util/log: re-allow switching away from stderr log file
* finish audio configuration rework
* cleanup HVF stubs
* remove more mentions of softmmu

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# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
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* tag 'for-upstream' of https://gitlab.com/bonzini/qemu: (25 commits)
  audio, qtest: get rid of QEMU_AUDIO_DRV
  audio: reintroduce default audio backend for VNC
  audio: do not use first -audiodev as default audio device
  audio: extend -audio to allow creating a default backend
  audio: extract audio_define_default
  audio: disable default backends if -audio/-audiodev is used
  audio: error hints need a trailing \n
  cutils: squelch compiler warnings with custom paths
  configure: change $softmmu to $system
  system: Rename softmmu/ directory as system/
  meson: Rename target_softmmu_arch -> target_system_arch
  meson: Rename softmmu_mods -> system_mods
  target/i386: Rename i386_softmmu_kvm_ss -> i386_kvm_ss
  semihosting: Rename softmmu_FOO_user() -> uaccess_FOO_user()
  gdbstub: Rename 'softmmu' -> 'system'
  accel: Rename accel_softmmu* -> accel_system*
  tcg: Correct invalid mentions of 'softmmu' by 'system-mode'
  fuzz: Correct invalid mentions of 'softmmu' by 'system'
  cpu: Correct invalid mentions of 'softmmu' by 'system-mode'
  travis-ci: Correct invalid mentions of 'softmmu' by 'system'
  ...

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'system/cpu-throttle.c')
-rw-r--r--system/cpu-throttle.c128
1 files changed, 128 insertions, 0 deletions
diff --git a/system/cpu-throttle.c b/system/cpu-throttle.c
new file mode 100644
index 0000000000..d9bb30a223
--- /dev/null
+++ b/system/cpu-throttle.c
@@ -0,0 +1,128 @@
+/*
+ * 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 "sysemu/cpus.h"
+#include "sysemu/cpu-throttle.h"
+
+/* vcpu throttling controls */
+static QEMUTimer *throttle_timer;
+static unsigned int throttle_percentage;
+
+#define CPU_THROTTLE_PCT_MIN 1
+#define CPU_THROTTLE_PCT_MAX 99
+#define CPU_THROTTLE_TIMESLICE_NS 10000000
+
+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_iothread(cpu->halt_cond,
+                                         sleeptime_ns / SCALE_MS);
+        } else {
+            qemu_mutex_unlock_iothread();
+            g_usleep(sleeptime_ns / SCALE_US);
+            qemu_mutex_lock_iothread();
+        }
+        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();
+
+    /* 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);
+}
+
+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_init(void)
+{
+    throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
+                                  cpu_throttle_timer_tick, NULL);
+}