Re: [Qemu-devel] [PATCH v4 1/5] cpu: Provide vcpu throttling interface

[Paolo Bonzini <pbonzini@redhat.com>]

On 02/07/2015 18:36, Jason J. Herne wrote:
> +static void cpu_throttle_thread(void *opaque)
> +{
> +    double pct = (double)throttle_percentage/100;
> +    double throttle_ratio = pct / (1 - pct);
> +    long sleeptime_ms = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE);
> +
> +    if (!throttle_percentage) {
> +        return;
> +    }
> +
> +    qemu_mutex_unlock_iothread();
> +    g_usleep(sleeptime_ms * 1000); /* Convert ms to us for usleep call */
> +    qemu_mutex_lock_iothread();
> +}
> +
> +static void cpu_throttle_timer_tick(void *opaque)
> +{
> +    CPUState *cpu;
> +
> +    /* Stop the timer if needed */
> +    if (!throttle_percentage) {
> +        return;
> +    }
> +    CPU_FOREACH(cpu) {
> +        async_run_on_cpu(cpu, cpu_throttle_thread, NULL);
> +    }
> +
> +    timer_mod(throttle_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) +
> +                                   CPU_THROTTLE_TIMESLICE);
> +}

This could cause callbacks to pile up I think.  David, do you have any
idea how to fix it?

Paolo