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Date:      Wed, 9 Jan 2002 10:45:10 +0200
From:      Peter Pentchev <roam@ringlet.net>
To:        Robert Watson <rwatson@FreeBSD.org>
Cc:        qa@FreeBSD.org
Subject:   Re: Reduced reliability due to larger socket queue defaults for TCP
Message-ID:  <20020109104509.C269@straylight.oblivion.bg>
In-Reply-To: <Pine.NEB.3.96L.1020108192957.32228A-100000@fledge.watson.org>; from rwatson@FreeBSD.org on Tue, Jan 08, 2002 at 07:33:25PM -0500
References:  <Pine.NEB.3.96L.1020106174749.96223A-100000@fledge.watson.org> <Pine.NEB.3.96L.1020108192957.32228A-100000@fledge.watson.org>

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On Tue, Jan 08, 2002 at 07:33:25PM -0500, Robert Watson wrote:
> The temptation here is one of two things:
> 
> (1) Back out the change increasing the send-q socket buffer size as a
>     default, and restore tuning(7) to recommend increasing the value, or
> 
> (2) To add the following text to the release notes:
> 
> 	In 4.5-RELEASE, default socket buffer sizes are increased to
> 	maximize performance on high speed networks.  However, under
> 	some circumstances, this can dramatically increase the memory
> 	requirements of the network system, requiring a manual
> 	bumping of the kernel NMBCLUSTERS setting.  This can be
> 	set using kern.ipc.nmbclusters.
> 
> My temptation is to bump back (1) a bit, possibly to bump up the keepalive
> rate, and stick in this note.  Reliability==good.

I personally feel better about (2)..  The buffer size increase really
does help with long-haul or high-latency connections.  Normal users
would rarely run thousands of TCP connections; those that do would
either read the release notes, or be kindly pointed to those.  People
who really do run thousands of TCP connections will hopefully read the
release notes and know what to do :)

As a side note, maybe this should be mentioned in the FAQ, too.

G'luck,
Peter

-- 
This sentence is false.

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