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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Wed, 1 Jul 2015 15:57:33 +0200
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Subject: Re: [Qemu-devel] [PATCH v3 1/5] cpu: Provide vcpu throttling
	interface
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To: "Jason J. Herne" <jjherne@linux.vnet.ibm.com>, afaerber@suse.de, amit.shah@redhat.com, dgilbert@redhat.com, borntraeger@de.ibm.com, quintela@redhat.com, qemu-devel@nongnu.org



On 25/06/2015 19:46, Jason J. Herne wrote:
> +static void cpu_throttle_thread(void *opaque)
> +{
> +    long sleeptime_ms = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE);
> +
> +    qemu_mutex_unlock_iothread();
> +    g_usleep(sleeptime_ms * 1000); /* Convert ms to us for usleep call */
> +    qemu_mutex_lock_iothread();
> +
> +    timer_mod(throttle_timer, qemu_clock_get_ms(QEMU_CLOCK_REALTIME) +
> +                                   CPU_THROTTLE_TIMESLICE);

The timer need not run while the VM is stopped.  Please use
QEMU_CLOCK_VIRTUAL_RT.

> +}
> +

Are you sure you want each CPU to set the timer?  I think this should be
done in cpu_throttle_timer_pop, or it could use timer_mod_anticipate.

> +static void cpu_throttle_timer_pop(void *opaque)
> +{
> +    CPUState *cpu;
> +
> +    /* Stop the timer if needed */
> +    if (throttle_timer_stop) {
> +        timer_del(throttle_timer);

timer_del is not needed in the timer callback.

Paolo

> +        timer_free(throttle_timer);
> +        throttle_timer = NULL;
> +        return;
> +    }
> +
> +    CPU_FOREACH(cpu) {
> +        async_run_on_cpu(cpu, cpu_throttle_thread, NULL);
> +    }
> +}
> +