From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH v2 net-next] tcp: switch rtt estimations to usec resolution
Date: Thu, 27 Feb 2014 21:20:25 -0800
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Cc: Julian Anastasov <ja@ssi.bg>, David Miller <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	Yuchung Cheng <ycheng@google.com>,
	Neal Cardwell <ncardwell@google.com>,
	Larry Brakmo <brakmo@google.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
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	(Eric Dumazet's message of "Sun, 23 Feb 2014 10:50:58 -0800")
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Eric Dumazet <eric.dumazet@gmail.com> writes:
>  
> -	rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt, sack_rtt);
> +	if (first_ackt.tv64) {
> +		ktime_t curt = ktime_get_real();

Sorry I'm late to the party. One problem is that if a system doesn't use
TSC for some reason this will be incredibly slow (unfortunately this
happens for various reasons). Perhaps we need a
ktime_get_real_but_use_jiffies_if_slow() or somesuch.

-andi

-- 
ak@linux.intel.com -- Speaking for myself only