netdev - Re: [PATCH] codel: refine one condition to avoid a nul rec_inv

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Date:	Mon, 30 Jul 2012 14:54:12 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, lp2s1h@...il.com
Subject: Re: [PATCH] codel: refine one condition to avoid a nul rec_inv_sqrt

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 30 Jul 2012 08:52:21 +0200

> From: Eric Dumazet <edumazet@...gle.com>
> 
> One condition before codel_Newton_step() was not good if
> we never left the dropping state for a flow. As a result
> rec_inv_sqrt was 0, instead of the ~0 initial value.
> 
> codel control law was then set to a very aggressive mode, dropping
> many packets before reaching 'target' and recovering from this problem.
> 
> To keep codel_vars_init() as efficient as possible, refine
> the condition to make sure rec_inv_sqrt initial value is correct
> 
> Many thanks to Anton Mich for discovering the issue and suggesting
> a fix.
> 
> Reported-by: Anton Mich <lp2s1h@...il.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable.
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