netdev - Re: [PATCH v6 net-next 2/2] tcp: switch rtt estimations to usec resolution

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Message-ID: <CADVnQymdZyE-Mb4F6QnTcJhHp4R9=GnYK9cTTpohQMFC=aK-Vw@mail.gmail.com>
Date:	Tue, 25 Feb 2014 14:13:24 -0500
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Stephen Hemminger <stephen@...workplumber.org>,
	Julian Anastasov <ja@....bg>,
	David Miller <davem@...emloft.net>,
	Yuchung Cheng <ycheng@...gle.com>,
	netdev <netdev@...r.kernel.org>, Larry Brakmo <brakmo@...gle.com>
Subject: Re: [PATCH v6 net-next 2/2] tcp: switch rtt estimations to usec resolution

On Tue, Feb 25, 2014 at 1:22 AM, Eric Dumazet <eric.dumazet@...il.com> 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.
>
> FQ/pacing in DC environments also require this change for finer control
> and removal of bimodal behavior due to the current hack in
> tcp_update_pacing_rate() for 'small rtt'
>
...
> ---
> v6: Do not use ktime_get() but skb_mstamp, as Stephen Hemminger pointed
>     out some platforms have slow ktime_get()
>
...
>  17 files changed, 174 insertions(+), 169 deletions(-)

> I think it is safe, because we made sure (sack_rtt_us >= 0) is true.

Sounds good. Thanks, Eric!

Acked-by: Neal Cardwell <ncardwell@...gle.com>

neal
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