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From: Neal Cardwell <>
To: Yuchung Cheng <>
Cc: David Miller <>,
	Eric Dumazet <>,
	Nandita Dukkipati <>,
	Netdev <>
Subject: Re: [PATCH 1/4 net-next] tcp: consolidate SYNACK RTT sampling
Date: Sun, 21 Jul 2013 22:45:13 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Sun, Jul 21, 2013 at 1:39 AM, Yuchung Cheng <> wrote:
> This patch series improve RTT sampling in three ways:
> 1. Sample RTT during fast recovery and reordering events.
> 2. Favor ack-based RTT to timestamps because of broken TS ECR fields
> 3. Consolidate the RTT measurement logic.
> The first patch consolidates SYNACK and other RTT measurement to use a
> central function tcp_ack_update_rtt(). A (small) bonus is now SYNACK
> RTT measurement happens after PAWS check, potentially reducing the
> impact of RTO seeding on bad TCP timestamps values.
> Signed-off-by: Yuchung Cheng <>

The idea seems very nice to me, but I think a line or two got dropped
in a rebase. :-)

In the previous version of this patch you moved the TFO-specific call
to tcp_synack_rtt_meas() out to a spot in tcp_rcv_state_process()
where both TFO and non-TFO passive connections would hit it. In this
version of the patch it removes the existing calls to
tcp_synack_rtt_meas() but does not add this new call to replace them.
(And it does not seem to be added back in a later patch in the

Other than that, looks great.


      parent reply	other threads:[~2013-07-22  2:45 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-21  5:39 Yuchung Cheng
2013-07-21  5:39 ` [PATCH 2/4 net-next] tcp: prefer packet timing to TS-ECR for RTT Yuchung Cheng
2013-07-22  3:17   ` Neal Cardwell
2013-07-21  5:39 ` [PATCH 3/4 net-next] tcp: measure RTT from new SACK Yuchung Cheng
2013-07-22  3:32   ` Neal Cardwell
2013-07-21  5:39 ` [PATCH 4/4 net-next] tcp: use RTT from SACK for RTO Yuchung Cheng
2013-07-22  3:40   ` Neal Cardwell
2013-07-22  2:45 ` Neal Cardwell [this message]

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