From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] tcp: cubic: fix bug in bictcp_acked()
Date: Wed, 07 Aug 2013 10:37:02 -0700 (PDT)
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From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 05 Aug 2013 20:05:12 -0700

> From: Eric Dumazet <edumazet@google.com>
> 
> While investigating about strange increase of retransmit rates
> on hosts ~24 days after boot, Van found hystart was disabled
> if ca->epoch_start was 0, as following condition is true
> when tcp_time_stamp high order bit is set.
> 
> (s32)(tcp_time_stamp - ca->epoch_start) < HZ
> 
> Quoting Van :
> 
>  At initialization & after every loss ca->epoch_start is set to zero so
>  I believe that the above line will turn off hystart as soon as the 2^31
>  bit is set in tcp_time_stamp & hystart will stay off for 24 days.
>  I think we've observed that cubic's restart is too aggressive without
>  hystart so this might account for the higher drop rate we observe.
> 
> Diagnosed-by: Van Jacobson <vanj@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied and queued up for -stable, thanks.