diff options
Diffstat (limited to 'migration/cpu-throttle.c')
| -rw-r--r-- | migration/cpu-throttle.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/migration/cpu-throttle.c b/migration/cpu-throttle.c new file mode 100644 index 0000000..0642e6b --- /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 "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); +} |