netdev - RE: [RFC PATCH net-next 0/3] sctp: add GSO support

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CCCEDE4@AcuExch.aculab.com>
Date:	Thu, 28 Jan 2016 13:51:02 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Marcelo Ricardo Leitner' <marcelo.leitner@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	Neil Horman <nhorman@...driver.com>,
	Vlad Yasevich <vyasevich@...il.com>,
	David Miller <davem@...emloft.net>,
	"brouer@...hat.com" <brouer@...hat.com>,
	"alexander.duyck@...il.com" <alexander.duyck@...il.com>,
	"alexei.starovoitov@...il.com" <alexei.starovoitov@...il.com>,
	"borkmann@...earbox.net" <borkmann@...earbox.net>,
	"marek@...udflare.com" <marek@...udflare.com>,
	"hannes@...essinduktion.org" <hannes@...essinduktion.org>,
	"fw@...len.de" <fw@...len.de>,
	"pabeni@...hat.com" <pabeni@...hat.com>,
	"john.r.fastabend@...el.com" <john.r.fastabend@...el.com>,
	"linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>
Subject: RE: [RFC PATCH net-next 0/3] sctp: add GSO support

From: Marcelo Ricardo Leitner
> Sent: 27 January 2016 17:07
> This patchset is merely a RFC for the moment. There are some
> controversial points that I'd like to discuss before actually proposing
> the patches.

You also need to look at how a 'user' can actually get SCTP to
merge data chunks in the first place.

With Nagle disabled (and it probably has to be since the data flow
is unlikely to be 'command-response' or 'unidirectional bulk')
it is currently almost impossible to get more than one chunk
into an ethernet frame.

Support for MSG_MORE would help.

Given the current implementation you can get almost the required
behaviour by turning nagle off and on repeatedly.

I did wonder whether the queued data could actually be picked up
be a Heartbeat chunk that is probing a different remote address
(which would be bad news).

	David