netdev - Re: [PATCH net-next 0/6] tcp: remove non GSO code

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Date:   Wed, 28 Feb 2018 17:10:18 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     edumazet@...gle.com, netdev@...r.kernel.org, ncardwell@...gle.com,
        ycheng@...gle.com, soheil@...gle.com, oleksandr@...alenko.name,
        eric.dumazet@...il.com, linux-sctp@...r.kernel.org
Subject: Re: [PATCH net-next 0/6] tcp: remove non GSO code

On Wed, Feb 21, 2018 at 02:37:48PM -0500, David Miller wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> Date: Mon, 19 Feb 2018 11:56:46 -0800
> 
> > Switching TCP to GSO mode, relying on core networking layers
> > to perform eventual adaptation for dumb devices was overdue.
> > 
> > 1) Most TCP developments are done with TSO in mind.
> > 2) Less high-resolution timers needs to be armed for TCP-pacing
> > 3) GSO can benefit of xmit_more hint
> > 4) Receiver GRO is more effective (as if TSO was used for real on sender)
> >    -> less ACK packets and overhead.
> > 5) Write queues have less overhead (one skb holds about 64KB of payload)
> > 6) SACK coalescing just works. (no payload in skb->head)
> > 7) rtx rb-tree contains less packets, SACK is cheaper.
> > 8) Removal of legacy code. Less maintenance hassles.
> > 
> > Note that I have left the sendpage/zerocopy paths, but they probably can
> > benefit from the same strategy.
> > 
> > Thanks to Oleksandr Natalenko for reporting a performance issue for BBR/fq_codel,
> > which was the main reason I worked on this patch series.
> 
> Series applied, thanks Eric.
> 
> SCTP might want to do something similar, and if so we can get rid
> of sk_can_gso() too.

Cc'ing linux-sctp and adding to the ToDo here, although it may be too
soon for SCTP. GSO support was added just a few months ago and
considering that it is not that much widely used as TCP, I fear we may
have some issues that didn't show up yet.

  Marcelo