From 2adcc85d407c1ab985f5abed808c78dbb84f4773 Mon Sep 17 00:00:00 2001 From: "Jason J. Herne" Date: Tue, 8 Sep 2015 13:12:33 -0400 Subject: [PATCH] cpu: Provide vcpu throttling interface Provide a method to throttle guest cpu execution. CPUState is augmented with timeout controls and throttle start/stop functions. To throttle the guest cpu the caller simply has to call the throttle set function and provide a percentage of throttle time. Signed-off-by: Jason J. Herne Reviewed-by: Matthew Rosato Signed-off-by: Juan Quintela Reviewed-by: Juan Quintela --- cpus.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/qom/cpu.h | 42 ++++++++++++++++++++++++++++++ 2 files changed, 120 insertions(+) diff --git a/cpus.c b/cpus.c index dddd056454..d44c0eda89 100644 --- a/cpus.c +++ b/cpus.c @@ -69,6 +69,14 @@ static CPUState *next_cpu; 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(); @@ -505,10 +513,80 @@ static const VMStateDescription vmstate_timers = { } }; +static void cpu_throttle_thread(void *opaque) +{ + CPUState *cpu = opaque; + double pct; + double throttle_ratio; + long sleeptime_ns; + + if (!cpu_throttle_get_percentage()) { + return; + } + + pct = (double)cpu_throttle_get_percentage()/100; + throttle_ratio = pct / (1 - pct); + sleeptime_ns = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS); + + qemu_mutex_unlock_iothread(); + atomic_set(&cpu->throttle_thread_scheduled, 0); + g_usleep(sleeptime_ns / 1000); /* Convert ns to us for usleep call */ + qemu_mutex_lock_iothread(); +} + +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, cpu); + } + } + + 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, NULL); vmstate_register(NULL, 0, &vmstate_timers, &timers_state); + throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT, + cpu_throttle_timer_tick, NULL); } void configure_icount(QemuOpts *opts, Error **errp) diff --git a/include/qom/cpu.h b/include/qom/cpu.h index 302673dbad..9405554a2b 100644 --- a/include/qom/cpu.h +++ b/include/qom/cpu.h @@ -321,6 +321,11 @@ struct CPUState { uint32_t can_do_io; int32_t exception_index; /* used by m68k TCG */ + /* Used to keep track of an outstanding cpu throttle thread for migration + * autoconverge + */ + bool throttle_thread_scheduled; + /* Note that this is accessed at the start of every TB via a negative offset from AREG0. Leave this field at the end so as to make the (absolute value) offset as small as possible. This reduces code @@ -565,6 +570,43 @@ CPUState *qemu_get_cpu(int index); */ bool cpu_exists(int64_t id); +/** + * cpu_throttle_set: + * @new_throttle_pct: Percent of sleep time. Valid range is 1 to 99. + * + * Throttles all vcpus by forcing them to sleep for the given percentage of + * time. A throttle_percentage of 25 corresponds to a 75% duty cycle roughly. + * (example: 10ms sleep for every 30ms awake). + * + * cpu_throttle_set can be called as needed to adjust new_throttle_pct. + * Once the throttling starts, it will remain in effect until cpu_throttle_stop + * is called. + */ +void cpu_throttle_set(int new_throttle_pct); + +/** + * cpu_throttle_stop: + * + * Stops the vcpu throttling started by cpu_throttle_set. + */ +void cpu_throttle_stop(void); + +/** + * cpu_throttle_active: + * + * Returns: %true if the vcpus are currently being throttled, %false otherwise. + */ +bool cpu_throttle_active(void); + +/** + * cpu_throttle_get_percentage: + * + * Returns the vcpu throttle percentage. See cpu_throttle_set for details. + * + * Returns: The throttle percentage in range 1 to 99. + */ +int cpu_throttle_get_percentage(void); + #ifndef CONFIG_USER_ONLY typedef void (*CPUInterruptHandler)(CPUState *, int); -- 2.11.4.GIT