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Re: [Qemu-devel] [PATCH v7 1/5] cpu: Provide vcpu throttling interface
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v7 1/5] cpu: Provide vcpu throttling interface |
Date: |
Wed, 9 Sep 2015 11:42:22 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 08/09/2015 19:12, Jason J. Herne wrote:
> 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 <address@hidden>
> Reviewed-by: Matthew Rosato <address@hidden>
Reviewed-by: Paolo Bonzini <address@hidden>
Acked-by: Paolo Bonzini <address@hidden>
Juan, please merge through your tree.
Paolo
> ---
> cpus.c | 78
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/qom/cpu.h | 42 ++++++++++++++++++++++++++++++
> 2 files changed, 120 insertions(+)
>
> diff --git a/cpus.c b/cpus.c
> index de6469f..b5ff9c9 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -68,6 +68,14 @@ 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();
> @@ -486,10 +494,80 @@ 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 39f0f19..db6ec1e 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -310,6 +310,11 @@ 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
> @@ -553,6 +558,43 @@ 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);
>
[Qemu-devel] [PATCH v7 3/5] migration: Dynamic cpu throttling for auto-converge, Jason J. Herne, 2015/09/08
Re: [Qemu-devel] [PATCH v7 0/5] migration: Dynamic cpu throttling for auto-converge, Juan Quintela, 2015/09/09