netdev - Re: [PATCH net] tcp: fix RTO calculated from cached RTT

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Message-ID: <1379420462.3457.11.camel@edumazet-glaptop>
Date:	Tue, 17 Sep 2013 05:21:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Neal Cardwell <ncardwell@...gle.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH net] tcp: fix RTO calculated from cached RTT

On Mon, 2013-09-16 at 21:44 -0400, Neal Cardwell wrote:
> Commit 1b7fdd2ab5852 ("tcp: do not use cached RTT for RTT estimation")
> did not correctly account for the fact that crtt is the RTT shifted
> left 3 bits. Fix the calculation to consistently reflect this fact.
> 
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Yuchung Cheng <ycheng@...gle.com>
> ---
>  net/ipv4/tcp_metrics.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Acked-by: Eric Dumazet <edumazet@...gle.com>

Instead of rto = 3*crtt, we had rto = 10*crtt, which was indeed
suboptimal ;)



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