Re: [Qemu-devel] [PATCH v3 3/3] util: Infrastructure for computing recent averages

[Paolo Bonzini <pbonzini@redhat.com>]

Il 24/09/2014 17:21, Benoît Canet ha scritto:
> The module takes care of computing minimal and maximal
> values over the time slice duration.

The code looks good, just two comments:

> +/* Get the average value
> + *
> + * @ta:  the timed average structure used
> + * @ret: the average value
> + */
> +uint64_t timed_average_avg(TimedAverage *ta)
> +{
> +    Window *w;
> +    check_expirations(ta);
> +
> +    w = current_window(ta);
> +
> +    if (w->count) {
> +        return w->sum / w->count;

First, do we want this to return double?

Second, this will return the min/max/avg in an unknown amount of time
between period/2 and period---on average period*3/4, e.g. 0.75 seconds
for a period equal to one second.

Would it make sense to tweak the TimedAverage period to be higher, e.g.
1.33 seconds/80 seconds/80 minutes, so that the _average_ period is 1
second/1 minute/1 hour?

This only applies to how the code is used, not to TimedAverage itself;
hence, feel free to post the patch with Reviewed-by once
timed_average_avg's return type is changed to a double.

Paolo

> +    }
> +
> +    return 0;
> +}
> +
> +/* Get the maximum value
> + *
> + * @ta:  the timed average structure used
> + * @ret: the maximal value
> + */
> +uint64_t timed_average_max(TimedAverage *ta)
> +{
> +    check_expirations(ta);
> +    return current_window(ta)->max;
> +}
>