netdev - Re: [PATCH v3 net-next] tcp: switch rtt estimations to usec resolution

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Message-ID: <1393264688.2316.65.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 24 Feb 2014 09:58:08 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Julian Anastasov <ja@....bg>
Cc:	Yuchung Cheng <ycheng@...gle.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Neal Cardwell <ncardwell@...gle.com>,
	Larry Brakmo <brakmo@...gle.com>
Subject: Re: [PATCH v3 net-next] tcp: switch rtt estimations to usec
 resolution

On Sun, 2014-02-23 at 20:42 -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> Upcoming congestion controls for TCP require usec resolution for RTT
> estimations. Millisecond resolution is simply not enough these days.
> ---
> v3: Also use usec resolution for samples provided by SACK, as Yuchung
> suggested. (I was planning to do this as a followup, but it seems
> better to do a single change)

I'll send a v4, switching to ktime_get() instead of ktime_get_real(),
because we need to be resistant to a change of time on the host,
notably for further changes (min_rtt and a change of TCP timestamp
resolution)



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