RE: [PATCH v4 3/6] latencystats: do not use floating point

["Morten Brørup" <mb@smartsharesystems.com>]

> +		if (unlikely(first_sample)) {
> +			first_sample = false;
> +
>  			glob_stats->min_latency = latency;
> -		else if (latency > glob_stats->max_latency)
>  			glob_stats->max_latency = latency;
> -		/*
> -		 * The average latency is measured using exponential moving
> -		 * average, i.e. using EWMA
> -		 * https://en.wikipedia.org/wiki/Moving_average
> -		 */
> -		glob_stats->avg_latency +=
> -			alpha * (latency - glob_stats->avg_latency);
> +			glob_stats->avg_latency = latency;
> +			glob_stats->jitter = latency / 2;

Setting jitter at first sample as latency / 2 is wrong.
Jitter should remain zero at first sample.

> +		} else {
> +			/*
> +			 * The jitter is calculated as statistical mean of
> interpacket
> +			 * delay variation. The "jitter estimate" is computed
> by taking
> +			 * the absolute values of the ipdv sequence and
> applying an
> +			 * exponential filter with parameter 1/16 to generate
> the
> +			 * estimate. i.e J=J+(|D(i-1,i)|-J)/16. Where J is
> jitter,
> +			 * D(i-1,i) is difference in latency of two
> consecutive packets
> +			 * i-1 and i.
> +			 * Reference: Calculated as per RFC 5481, sec 4.1,
> +			 * RFC 3393 sec 4.5, RFC 1889 sec.
> +			 */
> +			glob_stats->jitter += ((prev_latency - latency)
> +					       - glob_stats->jitter) / 16;

With jitter remaining zero at first sample,
Acked-by: Morten Brørup <mb@smartsharesystems.com>