From: Rick Jones <rick.jones2@hp•com>
To: David Laight <David.Laight@ACULAB•COM>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>
Subject: Re: Can I limit the number of active tx per TCP socket?
Date: Thu, 06 Mar 2014 09:17:37 -0800 [thread overview]
Message-ID: <5318ADB1.5050107@hp.com> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D0F6D3B91@AcuExch.aculab.com>
On 03/06/2014 04:28 AM, David Laight wrote:
> Is it possible to stop a TCP connection having more than one
> tx skb (in the ethernet tx ring) at any one time?
> The idea is to allow time for short sends from the application
> to accumulate so that the transmitted frames are longer.
That is precisely what Nagle is supposed to be doing - at least where
the definition of "time" is the round-trip-time rather than "time it
takes to get transmitted out the NIC."
> Basically I have a TCP connection which carries a lot of separate
> short 'user buffers'. These are not command-response so
> TCP_NODELAY has to be set to avoid long delays.
When you are saturating the receiver and/or the 64K line, are you
certain that not setting TCP_NODELAY means long delays?
From a later message:
> The data is sent out on a 64k line so 1ms is only 8 byte times.
Are you still using a 1460 byte MSS on such a connection?
Perhaps you can set the MSS (or drop the MTU on the 64K line and use
PTMU) to something less to trigger window updates a bit sooner and so
get piggy-backed ACKs rather than delayed ACKs and so not have to set
TCP_NODELAY? Yes, you will have a question of headers versus
headers+data but with TCP_NODELAY set as you have it you are (probably)
already trashing that.
Setting TCP_NODELAY to avoid "long delays" and then having a 64Kbyte/s
link seems a trifle, well, contradictory.
rick jones
next prev parent reply other threads:[~2014-03-06 17:17 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-06 12:28 Can I limit the number of active tx per TCP socket? David Laight
2014-03-06 14:15 ` John Heffner
2014-03-06 15:03 ` David Laight
2014-03-06 14:38 ` Eric Dumazet
2014-03-06 14:52 ` Eric Dumazet
2014-03-06 17:17 ` Rick Jones [this message]
2014-03-06 18:09 ` Neal Cardwell
2014-03-06 19:06 ` Rick Jones
2014-03-06 19:09 ` Neal Cardwell
2014-03-06 19:27 ` Eric Dumazet
2014-03-07 10:24 ` David Laight
2014-03-07 12:29 ` David Laight
2014-03-07 14:22 ` Eric Dumazet
2014-03-07 14:35 ` David Laight
2014-03-07 15:00 ` Eric Dumazet
2014-03-07 16:39 ` David Laight
2014-03-07 10:17 ` David Laight
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