Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period

[Peter Zijlstra]

On Wed, Jan 20, 2016 at 05:00:33PM +0100, Daniel Lezcano wrote:
> +static inline u32 stats_mean(struct stats *s)
> +{
> +	/*
> +	 * gcc is smart enough to convert to a bits shift when the
> +	 * divisor is constant and multiple of 2^x.
> +	 *
> +	 * The number of values could have not reached STATS_NR_VALUES
> +	 * yet, but we can consider it acceptable as the situation is
> +	 * only at the beginning of the burst of irqs.
> +	 */
> +	return s->sum / STATS_NR_VALUES;
> +}

Note that ->sum is u64, so you're very prone to truncation.