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

["Benoît Canet" <benoit.canet@nodalink.com>]

On Mon, Oct 13, 2014 at 02:05:34PM +0200, Paolo Bonzini wrote:
> 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.

This would require either changing _init period units or making it a float
or baking the 1.33 ratio in timed average.

Which one would you prefer ?

Best regards

Benoît

Thanks for reviewing.

> 
> 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;
> > +}
> > 
>