netdev - Re: [PATCH 0/2] sctp: Add GSO support

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Message-ID: <20160503114918.GD5676@localhost.localdomain>
Date:	Tue, 3 May 2016 08:49:18 -0300
From:	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, vyasevich@...il.com, nhorman@...driver.com,
	linux-sctp@...r.kernel.org, David.Laight@...LAB.COM,
	alexander.duyck@...il.com
Subject: Re: [PATCH 0/2] sctp: Add GSO support

On Mon, May 02, 2016 at 07:16:14PM -0400, David Miller wrote:
> From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Date: Fri, 29 Apr 2016 18:33:31 -0300
> 
> > This patchset adds sctp GSO support.
> > 
> > Performance tests indicates that increases throughput by 10% if using
> > bigger chunk sizes, specially if bigger than MTU. For small chunks, it
> > doesn't help much if not using heavy firewall rules.
> > 
> > For small chunks it will probably be of more use once we get something
> > like MSG_MORE as David Laight had suggested.
> > 
> > I believe I could address all comments from the RFC attempt.
> 
> Are these packets idempotent?
> 
> Ie. if we GRO a bunch of SCTP frames on receive and that GRO frame is
> forwarded rather than received locally, is the same exact packet
> stream emitted on transmit?

Forward path is not going to happen because we can't do GRO for SCTP,
unfortunatelly. We would have to somehow maintain frame boundaries (as
I did for GSO here) (so that AUTH chunks have a delimited scope, for
example) and that's not feasible with the current way we do GRO. Well,
at least I couldn't see how.

So this is just for pure tx path, no forwarding involved.

  Marcelo