1 files changed, 199 insertions, 0 deletions
diff --git a/migration/cpu-throttle.c b/migration/cpu-throttle.c
new file mode 100644
index 0000000000..5179019e33
--- /dev/null
+++ b/migration/cpu-throttle.c
@@ -0,0 +1,199 @@
+/*
+ * 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"
+#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);
+}