netdev - Re: [PATCH net] dctcp: more accurate tracking of packets delivery

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Message-Id: <20190411.213128.1944396160363371216.davem@davemloft.net>
Date:   Thu, 11 Apr 2019 21:31:28 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com, ycheng@...gle.com,
        ncardwell@...gle.com, soheil@...gle.com, fw@...len.de,
        daniel@...earbox.net, brakmo@...com, akabbani@...gle.com
Subject: Re: [PATCH net] dctcp: more accurate tracking of packets delivery

From: Eric Dumazet <edumazet@...gle.com>
Date: Thu, 11 Apr 2019 05:55:23 -0700

> After commit e21db6f69a95 ("tcp: track total bytes delivered with ECN CE marks")
> core TCP stack does a very good job tracking ECN signals.
> 
> The "sender's best estimate of CE information" Yuchung mentioned in his
> patch is indeed the best we can do.
> 
> DCTCP can use tp->delivered_ce and tp->delivered to not duplicate the logic,
> and use the existing best estimate.
> 
> This solves some problems, since current DCTCP logic does not deal with losses
> and/or GRO or ack aggregation very well.
> 
> This also removes a dubious use of inet_csk(sk)->icsk_ack.rcv_mss
> (this should have been tp->mss_cache), and a 64 bit divide.
> 
> Finally, we can see that the DCTCP logic, calling dctcp_update_alpha() for
> every ACK could be done differently, calling it only once per RTT.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks Eric.