cpu-throttle: new module, extracted from cpus.c

move the vcpu throttling functionality into its own module.

This functionality is not specific to any accelerator,
and it is used currently by migration to slow down guests to try to
have migrations converge, and by the cocoa MacOS UI to throttle speed.

cpu-throttle contains the controls to adjust and inspect throttle
settings, start (set) and stop vcpu throttling, and the throttling
function itself that is run periodically on vcpus to make them take a nap.

Execution of the throttling function on all vcpus is triggered by a timer,
registered at module initialization.

No functionality change.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20200629093504.3228-3-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 131 insertions, 87 deletions

diff --git a/softmmu/Makefile.objs b/softmmu/Makefile.objs
index a4bd9f2..a414a74 100644
--- a/softmmu/Makefile.objs
+++ b/softmmu/Makefile.objs
@@ -2,6 +2,7 @@ softmmu-main-y = softmmu/main.o
 
 obj-y += arch_init.o
 obj-y += cpus.o
+obj-y += cpu-throttle.o
 obj-y += balloon.o
 obj-y += ioport.o
 obj-y += memory.o
diff --git a/softmmu/cpu-throttle.c b/softmmu/cpu-throttle.c
new file mode 100644
index 0000000..4e6b281
--- /dev/null
+++ b/softmmu/cpu-throttle.c
@@ -0,0 +1,122 @@
+/*
+ * 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-common.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);
+    }
+    atomic_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 (!atomic_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)
+{
+    /* 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);
+
+    atomic_set(&throttle_percentage, new_throttle_pct);
+
+    timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
+                                       CPU_THROTTLE_TIMESLICE_NS);
+}
+
+void cpu_throttle_stop(void)
+{
+    atomic_set(&throttle_percentage, 0);
+}
+
+bool cpu_throttle_active(void)
+{
+    return (cpu_throttle_get_percentage() != 0);
+}
+
+int cpu_throttle_get_percentage(void)
+{
+    return atomic_read(&throttle_percentage);
+}
+
+void cpu_throttle_init(void)
+{
+    throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
+                                  cpu_throttle_timer_tick, NULL);
+}
diff --git a/softmmu/cpus.c b/softmmu/cpus.c
index d94456e..a802e89 100644
--- a/softmmu/cpus.c
+++ b/softmmu/cpus.c
@@ -61,6 +61,8 @@
 #include "hw/boards.h"
 #include "hw/hw.h"
 
+#include "sysemu/cpu-throttle.h"
+
 #ifdef CONFIG_LINUX
 
 #include <sys/prctl.h>
@@ -84,14 +86,6 @@ static QemuMutex qemu_global_mutex;
 int64_t max_delay;
 int64_t max_advance;
 
-/* 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
-
 bool cpu_is_stopped(CPUState *cpu)
 {
     return cpu->stopped || !runstate_is_running();
@@ -738,90 +732,12 @@ static const VMStateDescription vmstate_timers = {
     }
 };
 
-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(cpu->halt_cond, &qemu_global_mutex,
-                                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);
-    }
-    atomic_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 (!atomic_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)
-{
-    /* 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);
-
-    atomic_set(&throttle_percentage, new_throttle_pct);
-
-    timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
-                                       CPU_THROTTLE_TIMESLICE_NS);
-}
-
-void cpu_throttle_stop(void)
-{
-    atomic_set(&throttle_percentage, 0);
-}
-
-bool cpu_throttle_active(void)
-{
-    return (cpu_throttle_get_percentage() != 0);
-}
-
-int cpu_throttle_get_percentage(void)
-{
-    return atomic_read(&throttle_percentage);
-}
-
 void cpu_ticks_init(void)
 {
     seqlock_init(&timers_state.vm_clock_seqlock);
     qemu_spin_init(&timers_state.vm_clock_lock);
     vmstate_register(NULL, 0, &vmstate_timers, &timers_state);
-    throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
-                                           cpu_throttle_timer_tick, NULL);
+    cpu_throttle_init();
 }
 
 void configure_icount(QemuOpts *opts, Error **errp)
@@ -1879,6 +1795,11 @@ void qemu_cond_wait_iothread(QemuCond *cond)
     qemu_cond_wait(cond, &qemu_global_mutex);
 }
 
+void qemu_cond_timedwait_iothread(QemuCond *cond, int ms)
+{
+    qemu_cond_timedwait(cond, &qemu_global_mutex, ms);
+}
+
 static bool all_vcpus_paused(void)
 {
     CPUState *cpu;