netdev - Re: [PATCH v4 net-next] tcp: switch rtt estimations to usec resolution

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Date:	Mon, 24 Feb 2014 14:19:24 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	Yuchung Cheng <ycheng@...gle.com>, netdev <netdev@...r.kernel.org>,
	Neal Cardwell <ncardwell@...gle.com>,
	Larry Brakmo <brakmo@...gle.com>, Julian Anastasov <ja@....bg>
Subject: Re: [PATCH v4 net-next] tcp: switch rtt estimations to usec
 resolution

On Mon, 2014-02-24 at 10:24 -0800, Eric Dumazet wrote:


> index d547075d8300..8e4c43d80784 100644
> --- a/net/ipv4/tcp_metrics.c
> +++ b/net/ipv4/tcp_metrics.c

...

> -	if (crtt > tp->srtt) {
> +	if (crtt > tp->srtt_us) {
>  		/* Set RTO like tcp_rtt_estimator(), but from cached RTT. */
>  		crtt >>= 3;
> -		inet_csk(sk)->icsk_rto = crtt + max(2 * crtt, tcp_rto_min(sk));
> -	} else if (tp->srtt == 0) {

This part is buggy it needs to be :

	crtt /= 8 * USEC_PER_MSEC;
	inet_csk(sk)->icsk_rto = crtt + max(2 * crtt, tcp_rto_min(sk));


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