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Date:      Tue, 05 Feb 2013 18:44:27 +0100
From:      Andre Oppermann <andre@freebsd.org>
To:        John Baldwin <jhb@freebsd.org>
Cc:        Sepherosa Ziehau <sepherosa@gmail.com>, freebsd-net@freebsd.org, Bjoern Zeeb <bz@freebsd.org>
Subject:   Re: [PATCH] Add a new TCP_IGNOREIDLE socket option
Message-ID:  <511144FB.50807@freebsd.org>
In-Reply-To: <201302051211.43345.jhb@freebsd.org>
References:  <201301221511.02496.jhb@freebsd.org> <201301301158.33838.jhb@freebsd.org> <510957B9.8070203@freebsd.org> <201302051211.43345.jhb@freebsd.org>

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On 05.02.2013 18:11, John Baldwin wrote:
> On Wednesday, January 30, 2013 12:26:17 pm Andre Oppermann wrote:
>> You can simply create your own congestion control algorithm with only the
>> restart window changed.  See (pseudo) code below.  BTW, I just noticed that
>> the other cc algos don't do not reset the idle window.
>
> *sigh*  I am fully competent at maintaining my own local changes.  The point
> was to share this so that other people with similar workloads could make use
> of it.  Also, a custom CC algo is not the right approach as we would want this
> change regardless of the CC algo used for handling non-idle periods (so that
> this is an orthogonal knob).  Linux also makes this an orthogonal knob rather
> than requiring a separate CC algo.

If everything Linux does is good, then go ahead and commit it.  Discussing
this change further then is pointless.  I don't mind too much and I have
stated my case why I think it's the wrong thing to do.

I would prefer to encapsulate it into its own not-so-much-congestion-management
algorithm so you can eventually do other tweaks as well like more aggressive
loss recovery which would fit your objective as well.  Since you have to modify
your app anyways to do the sockopt call this seems a more complete solution to
me.  At least better than to do a non-portable hack that violates one of the
most fundamental TCP concepts.

-- 
Andre




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