netdev - Re: [PATCH net-next 0/7] tcp: implement rb-tree based retransmit queue

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Date:   Tue, 06 Feb 2018 07:52:18 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Laight <David.Laight@...LAB.COM>,
        'Eric Dumazet' <edumazet@...gle.com>,
        Tal Gilboa <talgi@...lanox.com>
Cc:     David Miller <davem@...emloft.net>,
        "ncardwell@...gle.com" <ncardwell@...gle.com>,
        "ycheng@...gle.com" <ycheng@...gle.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Amir Ancel <amira@...lanox.com>
Subject: Re: [PATCH net-next 0/7] tcp: implement rb-tree based retransmit
 queue

On Tue, 2018-02-06 at 15:22 +0000, David Laight wrote:
> From: Eric Dumazet
> > Sent: 06 February 2018 14:20
> 
> ...
> > Please give exact details.
> > Sending 64, 128, 256 or 512 bytes at a time on TCP_STREAM makes little sense.
> > We are not optimizing stack for pathological cases, sorry.
> 
> There are plenty of workloads which are not bulk data and where multiple
> small buffers get sent at unknown intervals (which may be back to back).
> Such connections have to have Nagle disabled because the Nagle delays
> are 'horrid'.
> Clearly lost packets can cause delays, but they are rare on local networks.

Auto corking makes sure aggregation happens, even for when Nagle is in
the picture.

netperf -- -m 256    will still cook 64KB TSO packets

netperf is not adding delays between each send(), unless it has been
modified.